sobeloperator.cpp revision 227b47625d7482b5b47ad0e4c70ce0a246236ade 
1/*
2 * Copyright (C) 2012 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// Native function to extract histogram from image (handed down as ByteBuffer).
18
19#include "sobeloperator.h"
20
21#include <math.h>
22#include <string.h>
23#include <jni.h>
24#include <unistd.h>
25#include <android/log.h>
26
27#include "imgprocutil.h"
28
29/*
30 * Perform 1d convolution on 3 channel image either horizontally or vertically.
31 * Parameters:
32 *  inputHead: pointer to input image
33 *  length: the length of image in the chosen axis.
34 *  fragments: number of lines of the image in the chosen axis.
35 *  step: the 1d pixel distance between adjacent pixels in the chosen axis.
36 *  shift: the 1d pixel distance between adjacent lines in the chosen axis.
37 *  filter: pointer to 1d filter
38 *  halfSize: the length of filter is supposed to be (2 * halfSize + 1)
39 *  outputHead: pointer to output image
40 */
41
42void computeGradient(unsigned char* dataPtr, int width, int height, short* gxPtr, short* gyPtr) {
43  for (int i = 0; i < height; i++) {
44    for (int j = 0; j < width; j++) {
45      const int left = (j > 0)? -4 : 0;
46      const int right = (j < width - 1) ? 4 : 0;
47      const int curr = (i * width + j) * 4;
48      const int above = (i > 0) ? curr - 4 * width : curr;
49      const int below = (i < height - 1) ? curr + 4 * width : curr;
50      const int offset = (i * width + j) * 3;
51      for (int c = 0; c < 3; c++) {
52        *(gxPtr + offset + c) =
53            (*(dataPtr + curr + c + right) - *(dataPtr + curr + c + left)) * 2 +
54            *(dataPtr + above + c + right) - *(dataPtr + above + c + left) +
55            *(dataPtr + below + c + right) - *(dataPtr + below + c + left);
56        *(gyPtr + offset + c) =
57            (*(dataPtr + c + below) - *(dataPtr + c + above)) * 2 +
58            *(dataPtr + left + c + below) - *(dataPtr + left + c + above) +
59            *(dataPtr + right + c + below) - *(dataPtr + right + c + above);
60      }
61    }
62  }
63}
64
65jboolean Java_androidx_media_filterpacks_image_SobelFilter_sobelOperator(
66    JNIEnv* env, jclass clazz, jint width, jint height, jobject imageBuffer,
67    jobject magBuffer, jobject dirBuffer) {
68
69  if (imageBuffer == 0) {
70    return JNI_FALSE;
71  }
72  unsigned char* srcPtr = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
73  unsigned char* magPtr = (magBuffer == 0) ?
74      0 : static_cast<unsigned char*>(env->GetDirectBufferAddress(magBuffer));
75  unsigned char* dirPtr = (dirBuffer == 0) ?
76      0 : static_cast<unsigned char*>(env->GetDirectBufferAddress(dirBuffer));
77
78  int numPixels = width * height;
79  // TODO: avoid creating and deleting these buffers within this native function.
80  short* gxPtr = new short[3 * numPixels];
81  short* gyPtr = new short[3 * numPixels];
82  computeGradient(srcPtr, width, height, gxPtr, gyPtr);
83
84  unsigned char* mag = magPtr;
85  unsigned char* dir = dirPtr;
86  for (int i = 0; i < numPixels; ++i) {
87    for (int c = 0; c < 3; c++) {
88      int gx = static_cast<int>(*(gxPtr + 3 * i + c) / 8 + 127.5);
89      int gy = static_cast<int>(*(gyPtr + 3 * i + c) / 8 + 127.5);
90
91      // emulate arithmetic in GPU.
92      gx = 2 * gx - 255;
93      gy = 2 * gy - 255;
94      if (magPtr != 0) {
95        double value = sqrt(gx * gx + gy * gy);
96        *(magPtr + 4 * i + c) = static_cast<unsigned char>(value);
97      }
98      if (dirPtr != 0) {
99        *(dirPtr + 4 * i + c) = static_cast<unsigned char>(
100            (atan(static_cast<double>(gy)/static_cast<double>(gx)) + 3.14) / 6.28);
101      }
102    }
103    //setting alpha change to 1.0 (255)
104    if (magPtr != 0) {
105      *(magPtr + 4 * i + 3) = 255;
106    }
107    if (dirPtr != 0) {
108      *(dirPtr + 4 * i + 3) = 255;
109    }
110  }
111
112  delete[] gxPtr;
113  delete[] gyPtr;
114
115  return JNI_TRUE;
116}
117