1f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 2f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * example.c 3f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 4f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * This file illustrates how to use the IJG code as a subroutine library 5f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * to read or write JPEG image files. You should look at this code in 69862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * conjunction with the documentation file libjpeg.txt. 7f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 8f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * This code will not do anything useful as-is, but it may be helpful as a 9f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * skeleton for constructing routines that call the JPEG library. 10f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 11f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * We present these routines in the same coding style used in the JPEG code 12f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (ANSI function definitions, etc); but you are of course free to code your 13f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * routines in a different style if you prefer. 14f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 15f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 16f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org#include <stdio.h> 17f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 18f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 19f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Include file for users of JPEG library. 20f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * You will need to have included system headers that define at least 21f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * the typedefs FILE and size_t before you can include jpeglib.h. 22f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (stdio.h is sufficient on ANSI-conforming systems.) 23f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * You may also wish to include "jerror.h". 24f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 25f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 26f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org#include "jpeglib.h" 27f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 28f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 29f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * <setjmp.h> is used for the optional error recovery mechanism shown in 30f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * the second part of the example. 31f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 32f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 33f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org#include <setjmp.h> 34f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 35f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 36f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 37f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/******************** JPEG COMPRESSION SAMPLE INTERFACE *******************/ 38f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 39f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* This half of the example shows how to feed data into the JPEG compressor. 40f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * We present a minimal version that does not worry about refinements such 41f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * as error recovery (the JPEG code will just exit() if it gets an error). 42f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 43f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 44f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 45f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 46f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * IMAGE DATA FORMATS: 47f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 48f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * The standard input image format is a rectangular array of pixels, with 49f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * each pixel having the same number of "component" values (color channels). 50f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Each pixel row is an array of JSAMPLEs (which typically are unsigned chars). 51f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * If you are working with color data, then the color values for each pixel 52f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * must be adjacent in the row; for example, R,G,B,R,G,B,R,G,B,... for 24-bit 53f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * RGB color. 54f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 55f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * For this example, we'll assume that this data structure matches the way 56f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * our application has stored the image in memory, so we can just pass a 57f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * pointer to our image buffer. In particular, let's say that the image is 58f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * RGB color and is described by: 59f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 60f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 61f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgextern JSAMPLE * image_buffer; /* Points to large array of R,G,B-order data */ 62f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgextern int image_height; /* Number of rows in image */ 63f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgextern int image_width; /* Number of columns in image */ 64f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 65f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 66f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 67f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Sample routine for JPEG compression. We assume that the target file name 68f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * and a compression quality factor are passed in. 69f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 70f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 71f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgGLOBAL(void) 72f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgwrite_JPEG_file (char * filename, int quality) 73f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org{ 74f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* This struct contains the JPEG compression parameters and pointers to 75f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * working space (which is allocated as needed by the JPEG library). 76f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * It is possible to have several such structures, representing multiple 77f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * compression/decompression processes, in existence at once. We refer 78f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * to any one struct (and its associated working data) as a "JPEG object". 79f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 80f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org struct jpeg_compress_struct cinfo; 81f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* This struct represents a JPEG error handler. It is declared separately 82f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * because applications often want to supply a specialized error handler 83f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (see the second half of this file for an example). But here we just 84f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * take the easy way out and use the standard error handler, which will 85f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * print a message on stderr and call exit() if compression fails. 86f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Note that this struct must live as long as the main JPEG parameter 87f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * struct, to avoid dangling-pointer problems. 88f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 89f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org struct jpeg_error_mgr jerr; 90f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* More stuff */ 91f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org FILE * outfile; /* target file */ 92f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */ 93f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org int row_stride; /* physical row width in image buffer */ 94f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 95f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 1: allocate and initialize JPEG compression object */ 96f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 97f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We have to set up the error handler first, in case the initialization 98f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * step fails. (Unlikely, but it could happen if you are out of memory.) 99f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * This routine fills in the contents of struct jerr, and returns jerr's 100f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * address which we place into the link field in cinfo. 101f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 102f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.err = jpeg_std_error(&jerr); 103f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Now we can initialize the JPEG compression object. */ 104f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_create_compress(&cinfo); 105f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 106f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 2: specify data destination (eg, a file) */ 107f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Note: steps 2 and 3 can be done in either order. */ 108f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 109f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Here we use the library-supplied code to send compressed data to a 110f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * stdio stream. You can also write your own code to do something else. 111f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that 112f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * requires it in order to write binary files. 113f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 114f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org if ((outfile = fopen(filename, "wb")) == NULL) { 115f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org fprintf(stderr, "can't open %s\n", filename); 116f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org exit(1); 117f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org } 118f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_stdio_dest(&cinfo, outfile); 119f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 120f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 3: set parameters for compression */ 121f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 122f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* First we supply a description of the input image. 123f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Four fields of the cinfo struct must be filled in: 124f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 125f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.image_width = image_width; /* image width and height, in pixels */ 126f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.image_height = image_height; 127f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.input_components = 3; /* # of color components per pixel */ 128f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.in_color_space = JCS_RGB; /* colorspace of input image */ 129f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Now use the library's routine to set default compression parameters. 130f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (You must set at least cinfo.in_color_space before calling this, 131f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * since the defaults depend on the source color space.) 132f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 133f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_set_defaults(&cinfo); 134f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Now you can set any non-default parameters you wish to. 135f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here we just illustrate the use of quality (quantization table) scaling: 136f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 137f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */); 138f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 139f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 4: Start compressor */ 140f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 141f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* TRUE ensures that we will write a complete interchange-JPEG file. 142f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Pass TRUE unless you are very sure of what you're doing. 143f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 144f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_start_compress(&cinfo, TRUE); 145f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 146f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 5: while (scan lines remain to be written) */ 147f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* jpeg_write_scanlines(...); */ 148f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 149f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Here we use the library's state variable cinfo.next_scanline as the 150f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * loop counter, so that we don't have to keep track ourselves. 151f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * To keep things simple, we pass one scanline per call; you can pass 152f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * more if you wish, though. 153f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 154f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org row_stride = image_width * 3; /* JSAMPLEs per row in image_buffer */ 155f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 156f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org while (cinfo.next_scanline < cinfo.image_height) { 157f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* jpeg_write_scanlines expects an array of pointers to scanlines. 158f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here the array is only one element long, but you could pass 159f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * more than one scanline at a time if that's more convenient. 160f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 161f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride]; 162f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (void) jpeg_write_scanlines(&cinfo, row_pointer, 1); 163f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org } 164f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 165f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 6: Finish compression */ 166f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 167f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_finish_compress(&cinfo); 168f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* After finish_compress, we can close the output file. */ 169f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org fclose(outfile); 170f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 171f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 7: release JPEG compression object */ 172f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 173f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* This is an important step since it will release a good deal of memory. */ 174f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_destroy_compress(&cinfo); 175f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 176f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* And we're done! */ 177f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org} 178f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 179f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 180f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 181f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * SOME FINE POINTS: 182f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 183f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * In the above loop, we ignored the return value of jpeg_write_scanlines, 184f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * which is the number of scanlines actually written. We could get away 185f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * with this because we were only relying on the value of cinfo.next_scanline, 186f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * which will be incremented correctly. If you maintain additional loop 187f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * variables then you should be careful to increment them properly. 188f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Actually, for output to a stdio stream you needn't worry, because 189f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * then jpeg_write_scanlines will write all the lines passed (or else exit 190f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * with a fatal error). Partial writes can only occur if you use a data 191f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * destination module that can demand suspension of the compressor. 192f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (If you don't know what that's for, you don't need it.) 193f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 194f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * If the compressor requires full-image buffers (for entropy-coding 195f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * optimization or a multi-scan JPEG file), it will create temporary 196f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * files for anything that doesn't fit within the maximum-memory setting. 197f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (Note that temp files are NOT needed if you use the default parameters.) 198f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * On some systems you may need to set up a signal handler to ensure that 1999862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * temporary files are deleted if the program is interrupted. See libjpeg.txt. 200f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 201f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Scanlines MUST be supplied in top-to-bottom order if you want your JPEG 202f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * files to be compatible with everyone else's. If you cannot readily read 203f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * your data in that order, you'll need an intermediate array to hold the 204f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * image. See rdtarga.c or rdbmp.c for examples of handling bottom-to-top 205f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * source data using the JPEG code's internal virtual-array mechanisms. 206f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 207f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 208f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 209f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 210f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/******************** JPEG DECOMPRESSION SAMPLE INTERFACE *******************/ 211f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 212f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* This half of the example shows how to read data from the JPEG decompressor. 213f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * It's a bit more refined than the above, in that we show: 214f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (a) how to modify the JPEG library's standard error-reporting behavior; 215f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (b) how to allocate workspace using the library's memory manager. 216f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 217f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Just to make this example a little different from the first one, we'll 218f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * assume that we do not intend to put the whole image into an in-memory 219f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * buffer, but to send it line-by-line someplace else. We need a one- 220f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * scanline-high JSAMPLE array as a work buffer, and we will let the JPEG 221f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * memory manager allocate it for us. This approach is actually quite useful 222f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * because we don't need to remember to deallocate the buffer separately: it 223f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * will go away automatically when the JPEG object is cleaned up. 224f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 225f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 226f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 227f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 228f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * ERROR HANDLING: 229f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 230f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * The JPEG library's standard error handler (jerror.c) is divided into 231f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * several "methods" which you can override individually. This lets you 232f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * adjust the behavior without duplicating a lot of code, which you might 233f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * have to update with each future release. 234f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 235f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Our example here shows how to override the "error_exit" method so that 236f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * control is returned to the library's caller when a fatal error occurs, 237f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * rather than calling exit() as the standard error_exit method does. 238f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 239f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * We use C's setjmp/longjmp facility to return control. This means that the 240f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * routine which calls the JPEG library must first execute a setjmp() call to 241f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * establish the return point. We want the replacement error_exit to do a 242f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * longjmp(). But we need to make the setjmp buffer accessible to the 243f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * error_exit routine. To do this, we make a private extension of the 244f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * standard JPEG error handler object. (If we were using C++, we'd say we 245f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * were making a subclass of the regular error handler.) 246f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 247f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here's the extended error handler struct: 248f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 249f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 250f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgstruct my_error_mgr { 251f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org struct jpeg_error_mgr pub; /* "public" fields */ 252f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 253f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jmp_buf setjmp_buffer; /* for return to caller */ 254f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org}; 255f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 256f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgtypedef struct my_error_mgr * my_error_ptr; 257f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 258f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 259f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here's the routine that will replace the standard error_exit method: 260f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 261f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 262f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgMETHODDEF(void) 263f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgmy_error_exit (j_common_ptr cinfo) 264f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org{ 265f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */ 266f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org my_error_ptr myerr = (my_error_ptr) cinfo->err; 267f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 268f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Always display the message. */ 269f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We could postpone this until after returning, if we chose. */ 270f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (*cinfo->err->output_message) (cinfo); 271f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 272f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Return control to the setjmp point */ 273f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org longjmp(myerr->setjmp_buffer, 1); 274f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org} 275f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 276f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 277f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 278f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Sample routine for JPEG decompression. We assume that the source file name 279f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * is passed in. We want to return 1 on success, 0 on error. 280f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 281f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 282f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 283f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgGLOBAL(int) 284f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.orgread_JPEG_file (char * filename) 285f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org{ 286f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* This struct contains the JPEG decompression parameters and pointers to 287f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * working space (which is allocated as needed by the JPEG library). 288f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 289f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org struct jpeg_decompress_struct cinfo; 290f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We use our private extension JPEG error handler. 291f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Note that this struct must live as long as the main JPEG parameter 292f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * struct, to avoid dangling-pointer problems. 293f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 294f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org struct my_error_mgr jerr; 295f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* More stuff */ 296f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org FILE * infile; /* source file */ 297f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org JSAMPARRAY buffer; /* Output row buffer */ 298f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org int row_stride; /* physical row width in output buffer */ 299f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 300f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* In this example we want to open the input file before doing anything else, 301f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * so that the setjmp() error recovery below can assume the file is open. 302f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that 303f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * requires it in order to read binary files. 304f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 305f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 306f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org if ((infile = fopen(filename, "rb")) == NULL) { 307f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org fprintf(stderr, "can't open %s\n", filename); 308f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org return 0; 309f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org } 310f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 311f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 1: allocate and initialize JPEG decompression object */ 312f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 313f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We set up the normal JPEG error routines, then override error_exit. */ 314f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org cinfo.err = jpeg_std_error(&jerr.pub); 315f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jerr.pub.error_exit = my_error_exit; 316f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Establish the setjmp return context for my_error_exit to use. */ 317f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org if (setjmp(jerr.setjmp_buffer)) { 318f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* If we get here, the JPEG code has signaled an error. 319f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * We need to clean up the JPEG object, close the input file, and return. 320f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 321f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_destroy_decompress(&cinfo); 322f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org fclose(infile); 323f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org return 0; 324f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org } 325f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Now we can initialize the JPEG decompression object. */ 326f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_create_decompress(&cinfo); 327f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 328f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 2: specify data source (eg, a file) */ 329f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 330f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_stdio_src(&cinfo, infile); 331f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 332f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 3: read file parameters with jpeg_read_header() */ 333f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 334f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (void) jpeg_read_header(&cinfo, TRUE); 335f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We can ignore the return value from jpeg_read_header since 336f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (a) suspension is not possible with the stdio data source, and 337f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * (b) we passed TRUE to reject a tables-only JPEG file as an error. 3389862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * See libjpeg.txt for more info. 339f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 340f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 341f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 4: set parameters for decompression */ 342f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 343f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* In this example, we don't need to change any of the defaults set by 344f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * jpeg_read_header(), so we do nothing here. 345f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 346f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 347f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 5: Start decompressor */ 348f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 349f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (void) jpeg_start_decompress(&cinfo); 350f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We can ignore the return value since suspension is not possible 351f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * with the stdio data source. 352f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 353f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 354f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We may need to do some setup of our own at this point before reading 355f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * the data. After jpeg_start_decompress() we have the correct scaled 356f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * output image dimensions available, as well as the output colormap 357f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * if we asked for color quantization. 358f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * In this example, we need to make an output work buffer of the right size. 359f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 360f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* JSAMPLEs per row in output buffer */ 361f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org row_stride = cinfo.output_width * cinfo.output_components; 362f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Make a one-row-high sample array that will go away when done with image */ 363f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org buffer = (*cinfo.mem->alloc_sarray) 364f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org ((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1); 365f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 366f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 6: while (scan lines remain to be read) */ 367f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* jpeg_read_scanlines(...); */ 368f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 369f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Here we use the library's state variable cinfo.output_scanline as the 370f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * loop counter, so that we don't have to keep track ourselves. 371f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 372f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org while (cinfo.output_scanline < cinfo.output_height) { 373f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* jpeg_read_scanlines expects an array of pointers to scanlines. 374f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here the array is only one element long, but you could ask for 375f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * more than one scanline at a time if that's more convenient. 376f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 377f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (void) jpeg_read_scanlines(&cinfo, buffer, 1); 378f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Assume put_scanline_someplace wants a pointer and sample count. */ 379f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org put_scanline_someplace(buffer[0], row_stride); 380f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org } 381f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 382f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 7: Finish decompression */ 383f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 384f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org (void) jpeg_finish_decompress(&cinfo); 385f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* We can ignore the return value since suspension is not possible 386f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * with the stdio data source. 387f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 388f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 389f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* Step 8: Release JPEG decompression object */ 390f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 391f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* This is an important step since it will release a good deal of memory. */ 392f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org jpeg_destroy_decompress(&cinfo); 393f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 394f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* After finish_decompress, we can close the input file. 395f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Here we postpone it until after no more JPEG errors are possible, 396f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * so as to simplify the setjmp error logic above. (Actually, I don't 397f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * think that jpeg_destroy can do an error exit, but why assume anything...) 398f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 399f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org fclose(infile); 400f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 401f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* At this point you may want to check to see whether any corrupt-data 402f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * warnings occurred (test whether jerr.pub.num_warnings is nonzero). 403f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 404f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 405f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org /* And we're done! */ 406f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org return 1; 407f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org} 408f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 409f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org 410f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org/* 411f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * SOME FINE POINTS: 412f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 413f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * In the above code, we ignored the return value of jpeg_read_scanlines, 414f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * which is the number of scanlines actually read. We could get away with 415f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * this because we asked for only one line at a time and we weren't using 4169862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * a suspending data source. See libjpeg.txt for more info. 417f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 418f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * We cheated a bit by calling alloc_sarray() after jpeg_start_decompress(); 419f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * we should have done it beforehand to ensure that the space would be 420f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * counted against the JPEG max_memory setting. In some systems the above 421f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * code would risk an out-of-memory error. However, in general we don't 422f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * know the output image dimensions before jpeg_start_decompress(), unless we 4239862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * call jpeg_calc_output_dimensions(). See libjpeg.txt for more about this. 424f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 425f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * Scanlines are returned in the same order as they appear in the JPEG file, 426f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * which is standardly top-to-bottom. If you must emit data bottom-to-top, 427f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * you can use one of the virtual arrays provided by the JPEG memory manager 428f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * to invert the data. See wrbmp.c for an example. 429f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * 430f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * As with compression, some operating modes may require temporary files. 431f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org * On some systems you may need to set up a signal handler to ensure that 4329862697206250265c6bb37a4186b0a411c78de3bhbono@chromium.org * temporary files are deleted if the program is interrupted. See libjpeg.txt. 433f0c4f33a4aa0760ba0e12a254b69d996442c9c5hbono@chromium.org */ 434