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UIImage+ImageProcessing.m
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UIImage+ImageProcessing.m
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//
// UIImage+ImageProcessing.m
//
// Created by Vincent Saluzzo on 28/05/12.
// Copyright (c) 2012. All rights reserved.
//
#import "UIImage+ImageProcessing.h"
@implementation UIImage (ImageProcessing)
- (UIImage *) toGrayscale
{
const int RED = 1;
const int GREEN = 2;
const int BLUE = 3;
// Create image rectangle with current image width/height
CGRect imageRect = CGRectMake(0, 0, self.size.width * self.scale, self.size.height * self.scale);
int width = imageRect.size.width;
int height = imageRect.size.height;
// the pixels will be painted to this array
uint32_t *pixels = (uint32_t *) malloc(width * height * sizeof(uint32_t));
// clear the pixels so any transparency is preserved
memset(pixels, 0, width * height * sizeof(uint32_t));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// create a context with RGBA pixels
CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * sizeof(uint32_t), colorSpace,
kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
// paint the bitmap to our context which will fill in the pixels array
CGContextDrawImage(context, CGRectMake(0, 0, width, height), [self CGImage]);
for(int y = 0; y < height; y++) {
for(int x = 0; x < width; x++) {
uint8_t *rgbaPixel = (uint8_t *) &pixels[y * width + x];
// convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
uint32_t gray = 0.3 * rgbaPixel[RED] + 0.59 * rgbaPixel[GREEN] + 0.11 * rgbaPixel[BLUE];
// set the pixels to gray
rgbaPixel[RED] = gray;
rgbaPixel[GREEN] = gray;
rgbaPixel[BLUE] = gray;
}
}
// create a new CGImageRef from our context with the modified pixels
CGImageRef image = CGBitmapContextCreateImage(context);
// we're done with the context, color space, and pixels
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
free(pixels);
// make a new UIImage to return
UIImage *resultUIImage = [UIImage imageWithCGImage:image
scale:self.scale
orientation:UIImageOrientationUp];
// we're done with image now too
CGImageRelease(image);
return resultUIImage;
}
- (UIImage *)tintWithColor:(UIColor *)tintColor
{
// Begin drawing
CGRect aRect = CGRectMake(0.f, 0.f, self.size.width, self.size.height);
CGImageRef alphaMask;
//
// Compute mask flipping image
//
{
UIGraphicsBeginImageContext(aRect.size);
CGContextRef c = UIGraphicsGetCurrentContext();
// draw image
CGContextTranslateCTM(c, 0, aRect.size.height);
CGContextScaleCTM(c, 1.0, -1.0);
[self drawInRect: aRect];
alphaMask = CGBitmapContextCreateImage(c);
UIGraphicsEndImageContext();
}
//
UIGraphicsBeginImageContext(aRect.size);
// Get the graphic context
CGContextRef c = UIGraphicsGetCurrentContext();
// Draw the image
[self drawInRect:aRect];
// Mask
CGContextClipToMask(c, aRect, alphaMask);
// Set the fill color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextSetFillColorSpace(c, colorSpace);
// Set the fill color
CGContextSetFillColorWithColor(c, tintColor.CGColor);
UIRectFillUsingBlendMode(aRect, kCGBlendModeNormal);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Release memory
CGColorSpaceRelease(colorSpace);
CGImageRelease(alphaMask);
return img;
}
@end