如何在现有图像上添加水印

Question

我找到了一些代码如下:

 UIGraphicsBeginImageContext(CGSizeMake(320, 480));
// This is where we resize captured image
[(UIImage *)[info objectForKey:UIImagePickerControllerOriginalImage] drawInRect:CGRectMake(0, 0, 320, 480)];
// And add the watermark on top of it
[[UIImage imageNamed:@"Watermark.png"] drawAtPoint:CGPointMake(0, 0) blendMode:kCGBlendModeNormal alpha:WATERMARK_ALPHA];
// Save the results directly to the image view property
imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

但我不确定这是否是最好的方式.

Answer 1

检查 CGImageCreateWithMask.

将现有图像和水印图像传递给此功能

- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

    CGImageRef maskRef = maskImage.CGImage; 

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                             CGImageGetHeight(maskRef),
                                        CGImageGetBitsPerComponent(maskRef),
                                        CGImageGetBitsPerPixel(maskRef),
                                        CGImageGetBytesPerRow(maskRef),
                                        CGImageGetDataProvider(maskRef), NULL, false);

    CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);

    return [UIImage imageWithCGImage:masked];

}