1 /*
2 * Copyright (C) 2013 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 contrast ratio from image (handed down as ByteBuffer).
18
19 #include "contrast.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 jfloat
Java_androidx_media_filterfw_samples_simplecamera_ContrastRatioFilter_contrastOperator(JNIEnv * env,jclass clazz,jint width,jint height,jobject imageBuffer)28 Java_androidx_media_filterfw_samples_simplecamera_ContrastRatioFilter_contrastOperator(
29 JNIEnv* env, jclass clazz, jint width, jint height, jobject imageBuffer) {
30
31 if (imageBuffer == 0) {
32 return 0.0f;
33 }
34 float total = 0;
35 const int numPixels = width * height;
36 unsigned char* srcPtr = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
37 float* lumArray = new float[numPixels];
38 for (int i = 0; i < numPixels; i++) {
39 lumArray[i] = (0.2126f * *(srcPtr + 4 * i) + 0.7152f *
40 *(srcPtr + 4 * i + 1) + 0.0722f * *(srcPtr + 4 * i + 2)) / 255;
41 total += lumArray[i];
42 }
43 const float avg = total / numPixels;
44 float sum = 0;
45
46 for (int i = 0; i < numPixels; i++) {
47 sum += (lumArray[i] - avg) * (lumArray[i] - avg);
48 }
49 delete[] lumArray;
50 return ((float) sqrt(sum / numPixels));
51 }
52