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
27jfloat
28Java_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