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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.
*/
// Native function to extract histogram from image (handed down as ByteBuffer).
#include "sobeloperator.h"
#include <math.h>
#include <string.h>
#include <jni.h>
#include <unistd.h>
#include <android/log.h>
#include "imgprocutil.h"
/*
* Perform 1d convolution on 3 channel image either horizontally or vertically.
* Parameters:
* inputHead: pointer to input image
* length: the length of image in the chosen axis.
* fragments: number of lines of the image in the chosen axis.
* step: the 1d pixel distance between adjacent pixels in the chosen axis.
* shift: the 1d pixel distance between adjacent lines in the chosen axis.
* filter: pointer to 1d filter
* halfSize: the length of filter is supposed to be (2 * halfSize + 1)
* outputHead: pointer to output image
*/
void computeGradient(unsigned char* dataPtr, int width, int height, short* gxPtr, short* gyPtr) {
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
const int left = (j > 0)? -4 : 0;
const int right = (j < width - 1) ? 4 : 0;
const int curr = (i * width + j) * 4;
const int above = (i > 0) ? curr - 4 * width : curr;
const int below = (i < height - 1) ? curr + 4 * width : curr;
const int offset = (i * width + j) * 3;
for (int c = 0; c < 3; c++) {
*(gxPtr + offset + c) =
(*(dataPtr + curr + c + right) - *(dataPtr + curr + c + left)) * 2 +
*(dataPtr + above + c + right) - *(dataPtr + above + c + left) +
*(dataPtr + below + c + right) - *(dataPtr + below + c + left);
*(gyPtr + offset + c) =
(*(dataPtr + c + below) - *(dataPtr + c + above)) * 2 +
*(dataPtr + left + c + below) - *(dataPtr + left + c + above) +
*(dataPtr + right + c + below) - *(dataPtr + right + c + above);
}
}
}
}
jboolean Java_androidx_media_filterpacks_image_SobelFilter_sobelOperator(
JNIEnv* env, jclass clazz, jint width, jint height, jobject imageBuffer,
jobject magBuffer, jobject dirBuffer) {
if (imageBuffer == 0) {
return JNI_FALSE;
}
unsigned char* srcPtr = static_cast<unsigned char*>(env->GetDirectBufferAddress(imageBuffer));
unsigned char* magPtr = (magBuffer == 0) ?
0 : static_cast<unsigned char*>(env->GetDirectBufferAddress(magBuffer));
unsigned char* dirPtr = (dirBuffer == 0) ?
0 : static_cast<unsigned char*>(env->GetDirectBufferAddress(dirBuffer));
int numPixels = width * height;
// TODO: avoid creating and deleting these buffers within this native function.
short* gxPtr = new short[3 * numPixels];
short* gyPtr = new short[3 * numPixels];
computeGradient(srcPtr, width, height, gxPtr, gyPtr);
unsigned char* mag = magPtr;
unsigned char* dir = dirPtr;
for (int i = 0; i < numPixels; ++i) {
for (int c = 0; c < 3; c++) {
int gx = static_cast<int>(*(gxPtr + 3 * i + c) / 8 + 127.5);
int gy = static_cast<int>(*(gyPtr + 3 * i + c) / 8 + 127.5);
// emulate arithmetic in GPU.
gx = 2 * gx - 255;
gy = 2 * gy - 255;
if (magPtr != 0) {
double value = sqrt(gx * gx + gy * gy);
*(magPtr + 4 * i + c) = static_cast<unsigned char>(value);
}
if (dirPtr != 0) {
*(dirPtr + 4 * i + c) = static_cast<unsigned char>(
(atan(static_cast<double>(gy)/static_cast<double>(gx)) + 3.14) / 6.28);
}
}
//setting alpha change to 1.0 (255)
if (magPtr != 0) {
*(magPtr + 4 * i + 3) = 255;
}
if (dirPtr != 0) {
*(dirPtr + 4 * i + 3) = 255;
}
}
delete[] gxPtr;
delete[] gyPtr;
return JNI_TRUE;
}
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