在Iphone中使圖像的觸摸區域透明

Question

我想使UIImage的觸摸像素透明。 我看到iPhone Objective C: How to get a pixel's color of the touched point on an UIImageView?

使用該代碼，我可以找到圖像觸摸像素。但我不知道如何使像素透明並更新UIImage。

請幫幫我。

Answer 1

希望這些可以幫助

What is the fastest way to draw single pixels directly to the screen in an iPhone application? 從這個SO質疑 How to get pixel data from a UIImage (Cocoa Touch) or CGImage (Core Graphics)?

+ (NSArray*)getRGBAsFromImage:(UIImage*)image atX:(int)xx andY:(int)yy count:(int)count 
{ 
    NSMutableArray *result = [NSMutableArray arrayWithCapacity: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 = malloc(height * width * 4); 
    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. 
    int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel; 
    for (int ii = 0 ; ii < count ; ++ii) 
    { 
     CGFloat red = (rawData[byteIndex]  * 1.0)/255.0; 
     CGFloat green = (rawData[byteIndex + 1] * 1.0)/255.0; 
     CGFloat blue = (rawData[byteIndex + 2] * 1.0)/255.0; 
     CGFloat alpha = (rawData[byteIndex + 3] * 1.0)/255.0; 
     byteIndex += 4; 

     UIColor *acolor = [UIColor colorWithRed:red green:green blue:blue alpha:alpha]; 
     [result addObject:acolor]; 
    } 

    free(rawData); 

    return result; 
}