as requested here is a fast decoding using NDK ( less then 10 ms on fast device ):
first here is the native.h
#include <jni.h>
#ifndef native_H
#define native_H
extern "C" {
JNIEXPORT jbyteArray JNICALL Com_example_MainActivity_nativeSetIamgeFromCamera(JNIEnv* jenv, jobject obj,jbyteArray array,jint length,jint x,jint y);
};
#endif
native.cpp
#include <stdint.h>
#include <jni.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <android/native_window.h>
#include <android/native_window_jni.h>
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include "native.h"
void Resize_and_decodyuv(unsigned char * data,int _width,int _height, unsigned char *out, int newWidth, int newHeight);
JNIEXPORT jbyteArray JNICALL Com_example_MainActivity_nativeSetIamgeFromCamera(JNIEnv* jenv, jobject obj,jbyteArray array,jint length,jint x,jint y)
{
//-----jbyteArray array contain the data from the camera passed by the java function
//-----length represent the size of jbyteArray in byte
//-----x,y respectively resolutionx and resolutiony of the image in jbyteArray array
unsigned char * buffImgCamera=(unsigned char *)malloc(length);
//----- copy the buffer from java array to c/c++ char * buffImgCamera
jenv->GetByteArrayRegion(array, 0, length, (jbyte*)buffImgCamera);
int width=400,height=600;//screen reso of the surface(400,800 is just an example)
unsigned char * buffOut=(unsigned char *)malloc(width*height*4);//prepare the result buffer where 4 represent R G B A(Alpha transparency channel).
//--- to gain time i decode and resize the image to fit the surface screen in one loop
Resize_and_decodyuv(buffImgCamera,x,y,buffOut,width,height);
//---copy the result to a jbytearray and return it to java function
jbyteArray result=env->NewByteArray(width*height*4);
env->SetByteArrayRegion( result, 0, width*height*4, buffOut);
return result;
}
void Resize_and_decodyuv(unsigned char * data,int _width,int _height, unsigned char *out, int newWidth, int newHeight)
{
int Colordeep=4;//RGBA; in the case of Qt Frame Work or Borland just put 3and the code should work;
float scaleWidth = (float)newWidth / (float)_width;
float scaleHeight = (float)newHeight / (float)_height;
for(int cy = 0; cy < newHeight; cy++)
{
for(int cx = 0; cx < newWidth; cx++)
{
int pixel = (cy * (newWidth *Colordeep)) + (cx*Colordeep);
int nearestMatch = ((((int)(cy / scaleHeight)) *_width) + (int)(cx /scaleWidth));
int cxa=cx/scaleWidth;
int cya=cy/scaleHeight; cya/=2;
int nearestMatch1 =(cya *_width) + (int)(cxa);
int y = ( data[nearestMatch]);
int v = data[data_uv+(nearestMatch1)];
int u = data[data_uv+(nearestMatch1)+1];
int r = (int) (1164 * (y - 16) + 1596 * (v - 128));
int g = (int) (1164 * (y - 16) - 813 * (v - 128) - 391 * (u - 128));
int b = (int) (1164 * (y - 16) + 2018 * (u - 128));
r/=1000;
g/=1000;
b/=1000;
r = r < 0 ? 0 : (r > 255 ? 255 : r);
g = g < 0 ? 0 : (g > 255 ? 255 : g);
b = b < 0 ? 0 : (b > 255 ? 255 : b);
out[pixel ] = r;
out[pixel +1 ] = g;
out[pixel + 2] = b;
if(Colordeep==4)out[pixel + 3] = 255;
}
}
}
java code
PreviewCallback previewCallback = new PreviewCallback () {
public void onPreviewFrame(byte[] data, Camera camera) {
//nativeSetIamgeFromCamera return a byte array
nativeSetIamgeFromCamera(data,data.length,camera.getParameters().getPreviewSize().width,camera.getParameters().getPreviewSize().height);
}
};