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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Stats (mean and stdev) scoring in the native.
#include "stats_scorer.h"
#include <jni.h>
#include <math.h>
void Java_androidx_media_filterpacks_numeric_StatsFilter_score(
JNIEnv* env, jobject thiz, jobject imageBuffer, jfloatArray statsArray)
{
unsigned char* pImg = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
int numPixels = env->GetDirectBufferCapacity(imageBuffer); // 1 byte per pixel
float sum = 0.0;
float sumSquares = 0.0;
for (int i = 0; i < numPixels; ++i) {
float val = static_cast<float>(pImg[i]);
sum += val;
sumSquares += val * val;
}
jfloat result[2];
result[0] = sum / numPixels; // mean
result[1] = sqrt((sumSquares - numPixels * result[0] * result[0]) / (numPixels - 1)); // stdev.
env->SetFloatArrayRegion(statsArray, 0, 2, result);
}
void Java_androidx_media_filterpacks_numeric_StatsFilter_regionscore(
JNIEnv* env, jobject thiz, jobject imageBuffer, jint width, jint height,
jfloat left, jfloat top, jfloat right, jfloat bottom, jfloatArray statsArray)
{
unsigned char* pImg = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
int xStart = static_cast<int>(width * left);
int xEnd = static_cast<int>(width * right);
int yStart = static_cast<int>(height * top);
int yEnd = static_cast<int>(height * bottom);
int numPixels = (xEnd - xStart) * (yEnd - yStart);
float sum = 0.0;
float sumSquares = 0.0;
for (int y = yStart; y < yEnd; y++) {
int disp = width * y;
for (int x = xStart; x < xEnd; ++x) {
float val = static_cast<float>(*(pImg + disp + x));
sum += val;
sumSquares += val * val;
}
}
jfloat result[2];
result[0] = sum / numPixels; // mean
result[1] = (numPixels == 1) ?
0 : sqrt((sumSquares - numPixels * result[0] * result[0]) / (numPixels - 1)); // stdev.
env->SetFloatArrayRegion(statsArray, 0, 2, result);
}
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