1/*
2* Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "Thumbnail.h"
18
19#define LOG_NDEBUG 0
20#define LOG_TAG "EmulatedCamera_Thumbnail"
21#include <cutils/log.h>
22#include <libexif/exif-data.h>
23#include <libyuv.h>
24
25#include "JpegCompressor.h"
26
27#include <vector>
28
29/*
30 * The NV21 format is a YUV format with an 8-bit Y-component and the U and V
31 * components are stored as 8 bits each but they are shared between a block of
32 * 2x2 pixels. So when calculating bits per pixel the 16 bits of U and V are
33 * shared between 4 pixels leading to 4 bits of U and V per pixel. Together
34 * with the 8 bits of Y this gives us 12 bits per pixel..
35 *
36 * The components are not grouped by pixels but separated into one Y-plane and
37 * one interleaved U and V-plane. The first half of the byte sequence is all of
38 * the Y data laid out in a linear fashion. After that the interleaved U and V-
39 * plane starts with one byte of V followed by one byte of U followed by one
40 * byte of V and so on. Each byte of U or V is associated with a 2x2 pixel block
41 * in a linear fashion.
42 *
43 * For an 8 by 4 pixel image the layout would be:
44 *
45 * +-----+-----+-----+-----+-----+-----+-----+-----+
46 * | Y0  | Y1  | Y2  | Y3  | Y4  | Y5  | Y6  | Y7  |
47 * +-----+-----+-----+-----+-----+-----+-----+-----+
48 * | Y8  | Y9  | Y10 | Y11 | Y12 | Y13 | Y14 | Y15 |
49 * +-----+-----+-----+-----+-----+-----+-----+-----+
50 * | Y16 | Y17 | Y18 | Y19 | Y20 | Y21 | Y22 | Y23 |
51 * +-----+-----+-----+-----+-----+-----+-----+-----+
52 * | Y24 | Y25 | Y26 | Y27 | Y28 | Y29 | Y30 | Y31 |
53 * +-----+-----+-----+-----+-----+-----+-----+-----+
54 * | V0  | U0  | V1  | U1  | V2  | U2  | V3  | U3  |
55 * +-----+-----+-----+-----+-----+-----+-----+-----+
56 * | V4  | U4  | V5  | U5  | V6  | U6  | V7  | U7  |
57 * +-----+-----+-----+-----+-----+-----+-----+-----+
58 *
59 * In this image V0 and U0 are the V and U components for the 2x2 block of
60 * pixels whose Y components are Y0, Y1, Y8 and Y9. V1 and U1 are matched with
61 * the Y components Y2, Y3, Y10, Y11, and so on for that row. For the next row
62 * of V and U the V4 and U4 components would be paired with Y16, Y17, Y24 and
63 * Y25.
64 */
65
66namespace android {
67
68static bool createRawThumbnail(const unsigned char* sourceImage,
69                               int sourceWidth, int sourceHeight,
70                               int thumbnailWidth, int thumbnailHeight,
71                               std::vector<unsigned char>* thumbnail) {
72    // Deinterleave the U and V planes into separate planes, this is because
73    // libyuv requires the planes to be separate when scaling
74    const size_t sourceUVPlaneSize = (sourceWidth * sourceHeight) / 4;
75    // Put both U and V planes in one buffer, one after the other, to reduce
76    // memory fragmentation and number of allocations
77    std::vector<unsigned char> sourcePlanes(sourceUVPlaneSize * 2);
78    const unsigned char* ySourcePlane = sourceImage;
79    unsigned char* uSourcePlane = &sourcePlanes[0];
80    unsigned char* vSourcePlane = &sourcePlanes[sourceUVPlaneSize];
81
82    for (size_t i = 0; i < sourceUVPlaneSize; ++i) {
83        vSourcePlane[i] = sourceImage[sourceWidth * sourceHeight + i * 2 + 0];
84        uSourcePlane[i] = sourceImage[sourceWidth * sourceHeight + i * 2 + 1];
85    }
86
87    // Create enough space in the output vector for the result
88    thumbnail->resize((thumbnailWidth * thumbnailHeight * 12) / 8);
89
90    // The downscaled U and V planes will also be linear instead of interleaved,
91    // allocate space for them here
92    const size_t destUVPlaneSize = (thumbnailWidth * thumbnailHeight) / 4;
93    std::vector<unsigned char> destPlanes(destUVPlaneSize * 2);
94    unsigned char* yDestPlane = &(*thumbnail)[0];
95    unsigned char* uDestPlane = &destPlanes[0];
96    unsigned char* vDestPlane = &destPlanes[destUVPlaneSize];
97
98    // The strides for the U and V planes are half the width because the U and V
99    // components are common to 2x2 pixel blocks
100    int result = libyuv::I420Scale(ySourcePlane, sourceWidth,
101                                   uSourcePlane, sourceWidth / 2,
102                                   vSourcePlane, sourceWidth / 2,
103                                   sourceWidth, sourceHeight,
104                                   yDestPlane, thumbnailWidth,
105                                   uDestPlane, thumbnailWidth / 2,
106                                   vDestPlane, thumbnailWidth / 2,
107                                   thumbnailWidth, thumbnailHeight,
108                                   libyuv::kFilterBilinear);
109    if (result != 0) {
110        ALOGE("Unable to create thumbnail, downscaling failed with error: %d",
111              result);
112        return false;
113    }
114
115    // Now we need to interleave the downscaled U and V planes into the
116    // output buffer to make it NV21 encoded
117    const size_t uvPlanesOffset = thumbnailWidth * thumbnailHeight;
118    for (size_t i = 0; i < destUVPlaneSize; ++i) {
119        (*thumbnail)[uvPlanesOffset + i * 2 + 0] = vDestPlane[i];
120        (*thumbnail)[uvPlanesOffset + i * 2 + 1] = uDestPlane[i];
121    }
122
123    return true;
124}
125
126bool createThumbnail(const unsigned char* sourceImage,
127                     int sourceWidth, int sourceHeight,
128                     int thumbWidth, int thumbHeight, int quality,
129                     ExifData* exifData) {
130    if (thumbWidth <= 0 || thumbHeight <= 0) {
131        ALOGE("%s: Invalid thumbnail width=%d or height=%d, must be > 0",
132              __FUNCTION__, thumbWidth, thumbHeight);
133        return false;
134    }
135
136    // First downscale the source image into a thumbnail-sized raw image
137    std::vector<unsigned char> rawThumbnail;
138    if (!createRawThumbnail(sourceImage, sourceWidth, sourceHeight,
139                            thumbWidth, thumbHeight, &rawThumbnail)) {
140        // The thumbnail function will log an appropriate error if needed
141        return false;
142    }
143
144    // And then compress it into JPEG format without any EXIF data
145    NV21JpegCompressor compressor;
146    status_t result = compressor.compressRawImage(&rawThumbnail[0],
147                                                  thumbWidth, thumbHeight,
148                                                  quality, nullptr /* EXIF */);
149    if (result != NO_ERROR) {
150        ALOGE("%s: Unable to compress thumbnail", __FUNCTION__);
151        return false;
152    }
153
154    // And finally put it in the EXIF data. This transfers ownership of the
155    // malloc'd memory to the EXIF data structure. As long as the EXIF data
156    // structure is free'd using the EXIF library this memory will be free'd.
157    exifData->size = compressor.getCompressedSize();
158    exifData->data = reinterpret_cast<unsigned char*>(malloc(exifData->size));
159    if (exifData->data == nullptr) {
160        ALOGE("%s: Unable to allocate %u bytes of memory for thumbnail",
161              __FUNCTION__, exifData->size);
162        exifData->size = 0;
163        return false;
164    }
165    compressor.getCompressedImage(exifData->data);
166    return true;
167}
168
169}  // namespace android
170
171