Change color of UIImage by pixel array - objective-c

Question

I want to change color of my image but dont want to change alpha of image.
I am using following code for change color in blue.
But i want to change image of all pixels array into perticuler RGB value.
Like I have to apply RGB value (R= 116 G=170 B= 243).
CGImageRef sourceImage = ImageView_Test.image.CGImage;
CFDataRef theData;
theData = CGDataProviderCopyData(CGImageGetDataProvider(sourceImage));
UInt8 *pixelData = (UInt8 *) CFDataGetBytePtr(theData);
int red = 0;
int green = 1;
int blue = 2;
int dataLength = CFDataGetLength(theData);
for (int index = 0; index < dataLength; index += 4)
{
if (pixelData[index + blue] - 80 > 0)
{
pixelData[index + red] = pixelData[index + blue] - 139;
pixelData[index + green] = pixelData[index + blue] - 85;
}
else
{
pixelData[index + green] = 0;
pixelData[index + red] = 0;
}
}
CGContextRef context;
context = CGBitmapContextCreate(pixelData,
CGImageGetWidth(sourceImage),
CGImageGetHeight(sourceImage),
8,
CGImageGetBytesPerRow(sourceImage),
CGImageGetColorSpace(sourceImage),
kCGImageAlphaPremultipliedLast);
CGImageRef newCGImage = CGBitmapContextCreateImage(context);
UIImage *newImage = [UIImage imageWithCGImage:newCGImage];
ImageView_Test.image = newImage;
CGContextRelease(context);
CFRelease(theData);
CGImageRelease(newCGImage);

Answer 1

I am using following method for change color of UIImage without affecting alpha of it.
-(UIImage *)didImageColorchanged:(NSString *)name withColor:(UIColor *)color
{
UIImage *img = [UIImage imageNamed:name];
UIGraphicsBeginImageContext(img.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[color setFill];
CGContextTranslateCTM(context, 0, img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetBlendMode(context, kCGBlendModeColorBurn);
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
CGContextDrawImage(context, rect, img.CGImage);
CGContextClipToMask(context, rect, img.CGImage);
CGContextAddRect(context, rect);
CGContextDrawPath(context,kCGPathFill);
UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return coloredImg;
}
Ex:
resultView.image = [self didImageColorchanged:[UIImage imageNamed:#"xyz.png"] withColor:[UIColor redColor]];

Answer 2

you can just use
// load image
UIImage *image = [UIImage imageNamed:#"test.png"];
CGImageRef imageRef = image.CGImage;
NSData *data = (NSData *)CGDataProviderCopyData(CGImageGetDataProvider(imageRef));
char *pixels = (char *)[data bytes];
// this is where you manipulate the individual pixels
// assumes a 4 byte pixel consisting of rgb and alpha
// for PNGs without transparency use i+=3 and remove int a
for(int i = 0; i < [data length]; i += 4)
{
int r = i;
int g = i+1;
int b = i+2;
int a = i+3;
pixels[r] = 0; // eg. remove red
pixels[g] = pixels[g];
pixels[b] = pixels[b];
pixels[a] = pixels[a];
}
// create a new image from the modified pixel data
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
size_t bitsPerPixel = CGImageGetBitsPerPixel(imageRef);
size_t bytesPerRow = CGImageGetBytesPerRow(imageRef);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, pixels, [data length], NULL);
CGImageRef newImageRef = CGImageCreate (
width,
height,
bitsPerComponent,
bitsPerPixel,
bytesPerRow,
colorspace,
bitmapInfo,
provider,
NULL,
false,
kCGRenderingIntentDefault
);
// the modified image
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// cleanup
free(pixels);
CGImageRelease(imageRef);
CGColorSpaceRelease(colorspace);
CGDataProviderRelease(provider);
CGImageRelease(newImageRef);