//
//  UIImage+ColorMasking.m
//  Cartographic
//
//  Created by Starla Insigna on 8/22/11.
//  Copyright 2011 Four Island. All rights reserved.
//

#import "UIImage+ColorMasking.h"

@implementation UIImage (ColorMasking)

typedef enum {
    ALPHA = 0,
    BLUE = 1,
    GREEN = 2,
    RED = 3
} PIXELS;

- (UIImage *)opaqueMaskFromWhiteImage
{
    CGSize size = [self size];
    int width = size.width;
    int height = 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];
            
            if ((rgbaPixel[RED] == 255) && (rgbaPixel[GREEN] == 255) && (rgbaPixel[BLUE] == 255) && (rgbaPixel[ALPHA] == 255))
            {
                rgbaPixel[RED] = 255;
                rgbaPixel[GREEN] = 255;
                rgbaPixel[BLUE] = 255;
                rgbaPixel[ALPHA] = 255;
            } else {
                rgbaPixel[RED] = 0;
                rgbaPixel[GREEN] = 0;
                rgbaPixel[BLUE] = 0;        
                rgbaPixel[ALPHA] = 0;
            }
        }
    }
    
    // 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];
    
    // we're done with image now too
    CGImageRelease(image);
    
    return resultUIImage;
}

@end