RGB in image processing in iphone app

Question

I am doing an image processing in mp app. I got the pixel color from image and apply this on image by touching.. My code get the pixel color but it changes the whole image in blue color and apply that blue in image processing. I am stuck in code. But don't know what is going wrong in my code.May you please help me.

My code is:

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{
UITouch *touch = [touches anyObject];
CGPoint coordinateTouch = [touch locationInView:[self view]];//where image was tapped

if (value == YES) {
    self.lastColor = [self getPixelColorAtLocation:coordinateTouch]; 
    value =NO;
}

NSLog(@"color %@",lastColor);
//[pickedColorDelegate pickedColor:(UIColor*)self.lastColor];



ListPoint point;
point.x = coordinateTouch.x;
point.y = coordinateTouch.y;

button = [UIButton buttonWithType:UIButtonTypeCustom];
button.backgroundColor = [UIColor whiteColor];
button.frame = CGRectMake(coordinateTouch.x-5, coordinateTouch.y-5, 2, 2);
//[descImageView addSubview:button];

[bgImage addSubview:button];

// Make image blurred on ImageView
if(bgImage.image)
{

    CGImageRef imgRef = [[bgImage image] CGImage];
    CFDataRef dataRef = CGDataProviderCopyData(CGImageGetDataProvider(imgRef)); 
    const unsigned char *sourceBytesPtr = CFDataGetBytePtr(dataRef);
    int len = CFDataGetLength(dataRef);
    NSLog(@"length = %d, width = %d, height = %d, bytes per row = %d, bit per pixels = %d", 
          len, CGImageGetWidth(imgRef), CGImageGetHeight(imgRef), CGImageGetBytesPerRow(imgRef), CGImageGetBitsPerPixel(imgRef));

    int width = CGImageGetWidth(imgRef);
    int height = CGImageGetHeight(imgRef);
    int widthstep = CGImageGetBytesPerRow(imgRef);
    unsigned char *pixelData = (unsigned char *)malloc(len);
    double wFrame = bgImage.frame.size.width;
    double hFrame = bgImage.frame.size.height;

    Image_Correction(sourceBytesPtr, pixelData, widthstep, width, height, wFrame, hFrame, point);

    NSLog(@"finish");


    NSData *data = [NSData dataWithBytes:pixelData length:len];

    NSLog(@"1");
    CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)data);

    NSLog(@"2");
    CGColorSpaceRef colorSpace2 = CGColorSpaceCreateDeviceRGB();

    NSLog(@"3");
    CGImageRef imageRef = CGImageCreate(width, height, 8, CGImageGetBitsPerPixel(imgRef), CGImageGetBytesPerRow(imgRef),
                                        colorSpace2,kCGImageAlphaNoneSkipFirst|kCGBitmapByteOrder32Host,
                                        provider, NULL, false, kCGRenderingIntentDefault);

    NSLog(@"Start processing image");
    UIImage *ret = [UIImage imageWithCGImage:imageRef scale:1.0 orientation:UIImageOrientationUp];
    CGImageRelease(imageRef);
    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpace2);
    CFRelease(dataRef);
    free(pixelData);
    NSLog(@"4");
    bgImage.image = ret;
    [button removeFromSuperview];
}   
}




- (UIColor*) getPixelColorAtLocation:(CGPoint)point {


UIColor* color = nil;
CGImageRef inImage = self.image.CGImage;
// Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, Blue
CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
if (cgctx == NULL) { return nil; /* error */ }

size_t w = CGImageGetWidth(inImage);
size_t h = CGImageGetHeight(inImage);
CGRect rect = {{0,0},{w,h}}; 

// Draw the image to the bitmap context. Once we draw, the memory 
// allocated for the context for rendering will then contain the 
// raw image data in the specified color space.
CGContextDrawImage(cgctx, rect, inImage); 

// Now we can get a pointer to the image data associated with the bitmap
// context.
unsigned char* data = CGBitmapContextGetData (cgctx);
if (data != NULL) {
    //offset locates the pixel in the data from x,y. 
    //4 for 4 bytes of data per pixel, w is width of one row of data.
    int offset = 4*((w*round(point.y))+round(point.x));
     alpha =  data[offset]; 
     red = data[offset+1]; 
     green = data[offset+2]; 
     blue = data[offset+3]; 
    NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);
    color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)];
}

// When finished, release the context
CGContextRelease(cgctx); 
// Free image data memory for the context
if (data) { free(data); }

return color;
}





- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {

CGContextRef    context = NULL;
CGColorSpaceRef colorSpace;
void *          bitmapData;
int             bitmapByteCount;
int             bitmapBytesPerRow;

// Get image width, height. We'll use the entire image.
size_t pixelsWide = CGImageGetWidth(inImage);
size_t pixelsHigh = CGImageGetHeight(inImage);

// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow   = (pixelsWide * 4);
bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

// Use the generic RGB color space.
colorSpace = CGColorSpaceCreateDeviceRGB();

if (colorSpace == NULL)
{
    fprintf(stderr, "Error allocating color space\n");
    return NULL;
}

// Allocate memory for image data. This is the destination in memory
// where any drawing to the bitmap context will be rendered.
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL) 
{
    fprintf (stderr, "Memory not allocated!");
    CGColorSpaceRelease( colorSpace );
    return NULL;
}

// Create the bitmap context. We want pre-multiplied ARGB, 8-bits 
// per component. Regardless of what the source image format is 
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
context = CGBitmapContextCreate (bitmapData,
                                 pixelsWide,
                                 pixelsHigh,
                                 8,      // bits per component
                                 bitmapBytesPerRow,
                                 colorSpace,
                                 kCGImageAlphaPremultipliedFirst);
if (context == NULL)
{
    free (bitmapData);
    fprintf (stderr, "Context not created!");
}

// Make sure and release colorspace before returning
CGColorSpaceRelease( colorSpace );

return context;
}



int Image_Correction(const unsigned char *pImage, unsigned char *rImage, int widthstep, int nW, int nH, double wFrame, double hFrame, ListPoint point)              

{
double ratiox = nW/wFrame;
double ratioy = nH/hFrame;
double newW, newH, ratio;
if(ratioy > ratiox)
{
    newH = hFrame;
    newW = nW/ratioy;
    ratio = ratioy;
}
else 
{
    newH = nH/ratiox;
    newW = wFrame;
    ratio = ratiox;
}
NSLog(@"new H, W = %f, %f", newW, newH);
NSLog(@"ratiox = %f; ratioy = %f", ratiox, ratioy);

ListPoint real_point;
real_point.x = (point.x - wFrame/2 + newW/2) *ratio;
real_point.y = (point.y - hFrame/2 + newH/2)*ratio;

for(int h = 0; h < nH; h++)
{
    for(int k = 0; k < nW; k++)
    {
        rImage[h*widthstep + k*4 + 0] = pImage[h*widthstep + k*4 + 0];
        rImage[h*widthstep + k*4 + 1] = pImage[h*widthstep + k*4 + 1];
        rImage[h*widthstep + k*4 + 2] = pImage[h*widthstep + k*4 + 2];
        rImage[h*widthstep + k*4 + 3] = pImage[h*widthstep + k*4 + 3];
    }
}

// Modify this parameter to change Blurred area
int iBlurredArea = 6;
for(int h = -ratio*iBlurredArea; h <= ratio*iBlurredArea; h++)
    for(int k = -ratio*iBlurredArea; k <= ratio*iBlurredArea; k++)
    {
        int tempx = real_point.x + k;
        int tempy = real_point.y + h;
        if (((tempy - 3) > 0)&&((tempy+3) >0)&&((tempx - 3) > 0)&&((tempx + 3) >0)) 
        {
            double sumR = 0;
            double sumG = 0;
            double sumB = 0;
            double sumA = 0; 
            double count = 0;
            for(int m = -3; m < 4; m++)
                for (int n = -3; n < 4; n++) 
                {                       
                    sumR = red;//sumR + pImage[(tempy + m)*widthstep + (tempx + n)*4 + 0];
                    sumG = green;//sumG + pImage[(tempy + m)*widthstep + (tempx + n)*4 + 1];
                    sumB = blue;//sumB + pImage[(tempy + m)*widthstep + (tempx + n)*4 + 2];
                    sumA = alpha;//sumA + pImage[(tempy + m)*widthstep + (tempx + n)*4 + 3];
                    count++;
                }



            rImage[tempy*widthstep + tempx*4 + 0] = red;//sumR/count;
            rImage[tempy*widthstep + tempx*4 + 1] = green;//sumG/count;
            rImage[tempy*widthstep + tempx*4 + 2] = blue;//sumB/count;
            rImage[tempy*widthstep + tempx*4 + 3] = alpha;//sumA/count;
        }
    }
return 1;
}

Thx for seeing this code.. i think i am doing something wrong. Thx in advance.

Answer 1

This seems to work for me.

UIImage* modifyImage(UIImage* image)
{
    size_t w = image.size.width;
    size_t h = image.size.height;
    CGFloat scale = image.scale;

    // Create the bitmap context
    UIGraphicsBeginImageContext(CGSizeMake(w*scale, h*scale));
    CGContextRef context = UIGraphicsGetCurrentContext();

    // NOTE you may have to setup a rotation here based on image.imageOrientation
    // but I didn't need to consider that for my images.
    CGContextScaleCTM(context, scale, scale);
    [image drawInRect:CGRectMake(0, 0, w, h)];

    unsigned char* data = CGBitmapContextGetData (context);
    if (data != NULL) {
        size_t height = CGBitmapContextGetHeight(context);
        size_t width = CGBitmapContextGetWidth(context);
        size_t bytesPerRow = CGBitmapContextGetBytesPerRow(context);

        for (int y = 0; y < height; y++) {
            for (int x = 0; x < width; x++) {
                // Not sure why the color info is in BGRA format
                // Look at CGBitmapContextGetBitmapInfo(context) if this format isn't working for you
                int offset = y * bytesPerRow + x * 4;
                unsigned char* blue =  &data[offset];
                unsigned char* green = &data[offset+1];
                unsigned char* red = &data[offset+2];
                unsigned char* alpha = &data[offset+3];

                int newRed = ...; // color calculation code here
                int newGreen = ...;
                int newBlue = ...;

                // Assuming you don't want to change the original alpha value.
                *red = (newRed * *alpha)/255;
                *green = (newGreen * *alpha)/255;
                *blue = (newBlue * *alpha)/255; 
            }               
        }
    }

    CGImageRef newImage = CGBitmapContextCreateImage(context);

    UIImage *done = [UIImage imageWithCGImage:newImage scale:image.scale orientation: image.imageOrientation];
    CGImageRelease(newImage);
    UIGraphicsEndImageContext();

    return done;
}