获取图片像素信息

- (NSArray*)getRGBAsFromImage:(UIImage*)image atX:(int)x andY:(int)y count:(int)count
{
    NSMutableArray *result = [[NSMutableArray alloc] initWithCapacity:count];
    
    // First get the image into your data buffer
    CGImageRef imageRef = [image CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char));
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                                 bitsPerComponent, bytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);
    
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);
    
    // Now your rawData contains the image data in the RGBA8888 pixel format.
    NSUInteger byteIndex = (bytesPerRow * y) + x * bytesPerPixel;
    for (int i = 0 ; i < count ; ++i)
    {
        CGFloat alpha = ((CGFloat) rawData[byteIndex + 3] ) / 255.0f;
        CGFloat red   = ((CGFloat) rawData[byteIndex]     ) / alpha;
        CGFloat green = ((CGFloat) rawData[byteIndex + 1] ) / alpha;
        CGFloat blue  = ((CGFloat) rawData[byteIndex + 2] ) / alpha;
        byteIndex += bytesPerPixel;
        
        UIColor *acolor = [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
        
        [result addObject:acolor];
    }
    free(rawData);
    
    return result;
}

http://stackoverflow.com/questions/448125/how-to-get-pixel-data-from-a-uiimage-cocoa-touch-or-cgimage-core-graphics

__block NSString *leftStr = @"FirstLeft";

    

    NSString *centrStr = @"FirstCenter";

    

    NSString* (^myBlock)(NSString *) = ^(NSString *lastStr){

        

        return [leftStr stringByAppendingString:[NSString stringWithFormat:@", %@, %@", centrStr, lastStr]];

    };

    

    NSLog(@"%@", myBlock(@"last"));

    

    leftStr = @"ThenLeft";

    centrStr = @"ThenCenter";

    

    NSLog(@"%@", myBlock(@"right"));