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 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
