Image Processing - How to find a pixel cordinates in iOS ?

Question

Hi,
I want to know how to find the cordinates of the pixel which i am chaging.
Here is what i am doing.
CGImageRef imgSource = self.ImageView.image.CGImage;
    CFDataRef m_DataRed1 = CGDataProviderCopyData(CGImageGetDataProvider(imgSource));
    CGFloat myheight;
    CGFloat mywidth;
    myheight= CGImageGetHeight(imgSource);
    mywidth = CGImageGetWidth(imgSource);
    UInt8 *dataOrignal = (UInt8 *)CFDataGetBytePtr(m_DataRed1);
    double lenghtSource = CFDataGetLength(m_DataRed1);
    NSLog(@"lenght : %f",lenghtSource);
    int bytesPerPixel_ = CGImageGetBitsPerPixel(imgSource)/8;
    size_t bytesPerRow = CGImageGetBytesPerRow(imgSource);
    NSLog(@"height = %f, width = %f, bytesperPixel = %d",myheight,mywidth,bytesPerPixel_);
    for(int x = 0; x < myheight; x++)
        for(int y = 0; y < mywidth; y++)
            int pixelStartIndex = bytesPerPixel_*((bytesPerRow*x)+y);
//            if (pixelStartIndex <= lenghtSource) {
                UInt8 alphaVal = dataOrignal[pixelStartIndex];
                UInt8 redVal = dataOrignal[pixelStartIndex + 1];
                UInt8 greenVal = dataOrignal[pixelStartIndex + 2];
                UInt8 blueVal = dataOrignal[pixelStartIndex + 3];
                if(redVal == 236 || alphaVal == 236 || greenVal == 236)
                    dataOrignal[pixelStartIndex] = 255;
                    dataOrignal[pixelStartIndex +1] = 0;
                    dataOrignal[pixelStartIndex +2] = 0;
                    dataOrignal[pixelStartIndex+3]= 255;
                    NSLog(@"x %d, y = %d, index = %d", x, y,pixelStartIndex);
    NSUInteger width = CGImageGetWidth(imgSource); //202
    NSUInteger height = CGImageGetHeight(imgSource);//173
    size_t bitsPerComponent = CGImageGetBitsPerComponent(imgSource);
    size_t bitsPerPixel = CGImageGetBitsPerPixel(imgSource);
    NSLog(@"the width = %u and height=%u of the image is ",width,height );
    NSLog(@"the bits per component is %zd", bitsPerComponent);
    NSLog(@"the bits per pixel is %zd", bitsPerPixel);
    NSLog(@"the bytes per row is %zd" , bytesPerRow);
    CGColorSpaceRef colorspace = CGImageGetColorSpace(imgSource);
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imgSource);
    CFDataRef newData = CFDataCreate(NULL, dataOrignal, lenghtSource);
    CGDataProviderRef provider = CGDataProviderCreateWithCFData(newData);
    CGContextRef context = CGBitmapContextCreate(newData, width, height, bitsPerComponent, bytesPerRow, colorspace, bitmapInfo);
    CGPoint point = CGContextGetTextPosition(context);
    NSInteger xx =  point.x;
//    point.y;
    NSLog(@"this is the value of x axis %d",xx);
    CGImageRef newImg = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorspace, bitmapInfo, provider, NULL, true, kCGRenderingIntentDefault);
    UIImage *newImage1 = [UIImage imageWithCGImage:newImg];
    self.ImageView.image = newImage1;
is this the right way to parse the image using x & y ?
I dont know if the pixelstartIndex is correct or not, but it does change the pixels.
I want to make sure if the x & y i am NSLogging is correct or not.
Thanks in Advance

Answer 1

BufferedImage img = null;
DataBufferByte imgRasterBuffer = null;
int imgColors[][];
URL url = BumpMap1.class.getResource("bumpmap1/img.png");
try
img = ImageIO.read(url);
catch(java.io.IOException x)
System.out.println(x.getMessage());
imgWidth = img.getWidth();
imgHeight = img.getHeight();
imgRasterBuffer = (DataBufferByte)(img.getRaster().getDataBuffer());
imgColors = new int[imgWidth * imgHeight][3];
// Store RGB values into array
for (int x = 0; x < imgWidth; x++)
for (int y = 0; y < imgHeight; y++)
int c = img.getRGB(x, y);
int loc = y * imgWidth + x;
imgColors[loc][0] = (c&(255<<16))>>16;
imgColors[loc][1] = (c&(255<<8))>>8;
imgColors[loc][2] = c&255;
if(imgColors[pixX+(pixY*imgWidth)][0] == 0 &&
imgColors[pixX+(pixY*imgWidth)][1] == 0 &&
imgColors[pixX+(pixY*imgWidth)][2] == 0)
// it's black