Color Table

gistfile1.m

//
//  HRAppDelegate.m
//  ColorTableTest
//
//  Created by Patrick Rogers on 1/17/12.
//  Copyright (c) 2012 Hello Resolven. All rights reserved.
//

#import "HRAppDelegate.h"

// 1 will produce correctly colored GIF, 2 will produce wrongly colored GIF.

#define NUMBER_OF_FRAMES 2

@implementation HRAppDelegate

@synthesize window = _window;


// create image from path
- (CGImageRef)imageWithPath:(NSString *)path {
    CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef)[NSData dataWithContentsOfFile:path]);
    CGImageRef image = CGImageCreateWithPNGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);
    return image;
}


// properties to be applied to each frame... such as setting delay time & color map.

- (NSDictionary *)frameProperties {
    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:5];
    [dict setObject:[NSNumber numberWithFloat:0.5] forKey:(NSString *)kCGImagePropertyGIFDelayTime];
    
    const uint8_t colorTable[ 9 ] = { 0, 0, 0, 128, 128, 128, 255,255,255};
    NSData* colorTableData = [ NSData dataWithBytes: colorTable length: 9 ];
    
    [dict setObject:colorTableData forKey:(NSString *)kCGImagePropertyGIFImageColorMap];
    
    NSDictionary *frameProps = [ NSDictionary dictionaryWithObject: dict 
                                                          forKey: (NSString*) kCGImagePropertyGIFDictionary ];
    
    return frameProps;
}

// properties to apply to entire GIF... such as loop count (0 = infinite) and no global color map.

- (NSDictionary *)gifProperties {
    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:5];
    
    [dict setObject:[NSNumber numberWithBool:NO] forKey:(NSString *)kCGImagePropertyGIFHasGlobalColorMap];
    [dict setObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount];

    NSDictionary *gifProps = [ NSDictionary dictionaryWithObject: dict 
                                                            forKey: (NSString*) kCGImagePropertyGIFDictionary ];
    
    return gifProps;
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    
    // load images
    NSString *pathOne = [[NSBundle mainBundle] pathForImageResource:@"one"];
    NSString *pathTwo = [[NSBundle mainBundle] pathForImageResource:@"two"];
    
    CGImageRef imageOne = [self imageWithPath:pathOne];
    CGImageRef imageTwo = [self imageWithPath:pathTwo];
    
    // output final gif to desktop.

    NSURL *destUrl = [NSURL fileURLWithPath:[@"~/Desktop/test.gif" stringByExpandingTildeInPath]];
    
    CGImageDestinationRef dst = CGImageDestinationCreateWithURL( (__bridge CFURLRef) destUrl, kUTTypeGIF, NUMBER_OF_FRAMES, NULL );
    
    // add first image.
    
    CGImageDestinationAddImage( dst, imageOne, (__bridge CFDictionaryRef) [self frameProperties] );
    
    // add second image if NUMBER_OF_FRAMES is 2... set to 1 see the kCGImagePropertyGIFImageColorMap property actually work.
    
#if (NUMBER_OF_FRAMES == 2)
    NSLog(@"adding second one.");
    CGImageDestinationAddImage( dst, imageTwo, (__bridge CFDictionaryRef) [self frameProperties] );
#endif
    
    CGImageDestinationSetProperties(dst, (__bridge CFDictionaryRef) [self gifProperties]);
    
    CGImageDestinationFinalize( dst );
    
    // cleanup
    
    CFRelease(imageTwo);
    CFRelease(imageOne);
    CFRelease( dst );
}

@end