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// Stats (mean and stdev) scoring in the native.
18
19#include "stats_scorer.h"
20
21#include <jni.h>
22#include <math.h>
23
24void Java_androidx_media_filterpacks_numeric_StatsFilter_score(
25    JNIEnv* env, jobject thiz, jobject imageBuffer, jfloatArray statsArray)
26{
27    unsigned char* pImg = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
28    int numPixels  = env->GetDirectBufferCapacity(imageBuffer);  // 1 byte per pixel
29    float sum = 0.0;
30    float sumSquares = 0.0;
31
32    for (int i = 0; i < numPixels; ++i) {
33        float val = static_cast<float>(pImg[i]);
34        sum += val;
35        sumSquares += val * val;
36    }
37    jfloat result[2];
38    result[0] = sum / numPixels;  // mean
39    result[1] = sqrt((sumSquares - numPixels * result[0] * result[0]) / (numPixels - 1));  // stdev.
40    env->SetFloatArrayRegion(statsArray, 0, 2, result);
41}
42
43void Java_androidx_media_filterpacks_numeric_StatsFilter_regionscore(
44    JNIEnv* env, jobject thiz, jobject imageBuffer, jint width, jint height,
45    jfloat left, jfloat top, jfloat right, jfloat bottom, jfloatArray statsArray)
46{
47    unsigned char* pImg = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
48    int xStart = static_cast<int>(width * left);
49    int xEnd = static_cast<int>(width * right);
50    int yStart = static_cast<int>(height * top);
51    int yEnd = static_cast<int>(height * bottom);
52    int numPixels  = (xEnd - xStart) * (yEnd - yStart);
53    float sum = 0.0;
54    float sumSquares = 0.0;
55
56    for (int y = yStart; y < yEnd; y++) {
57      int disp = width * y;
58      for (int x = xStart; x < xEnd; ++x) {
59        float val = static_cast<float>(*(pImg + disp + x));
60        sum += val;
61        sumSquares += val * val;
62      }
63    }
64    jfloat result[2];
65    result[0] = sum / numPixels;  // mean
66    result[1] = (numPixels == 1) ?
67        0 : sqrt((sumSquares - numPixels * result[0] * result[0]) / (numPixels - 1));  // stdev.
68    env->SetFloatArrayRegion(statsArray, 0, 2, result);
69}
70
71