如何在iOS的uiimage中找到透明区域？

Question

Hi Friends, I am developing color filling game.i know how to color in full image.but i want to color the image in transparent area.

Here my code for coloring image

-(UIImage*)setCollor:(UIColor*)color image:(UIImage*)img
{
    UIGraphicsBeginImageContext(img.size);    
    CGContextRef context = UIGraphicsGetCurrentContext();

    // set the fill color
    [color setFill];

    CGContextTranslateCTM(context, 0, img.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // set the blend mode to color burn, and the original image
    CGContextSetBlendMode(context, kCGBlendModeColorBurn);
    CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
    CGContextDrawImage(context, rect, img.CGImage);

    // set a mask that matches the shape of the image, then draw (color burn) a colored rectangle
    CGContextClipToMask(context, rect, img.CGImage);
    CGContextAddRect(context, rect);
    CGContextDrawPath(context,kCGPathFill);

    // generate a new UIImage from the graphics context we drew onto
    UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    //return the color-burned image
    return coloredImg;
}

How to find transparent area in the image and fill the colors..?

Answer 1

First fill the color for complete rect. The rect will be of size image width and image height. Now draw the image on same rect.

    CGContextSetFillColorWithColor( context, [UIColor redColor].CGColor );
    CGContextFillRect( context, rect );

    CGContextDrawImage(context, rect, [UIImage imageNamed:@"myImage"].CGImage);