iPhone，一张图像叠加到另一张图像上以创建要保存的新图像?(水印)
问题说明
基本上，我想拍摄用户从他们的照片库中选择的图像，然后应用水印，右下角有一个三角形，上面有应用程序名称.我已经在 Photoshop 中使用透明图层制作了第二张图像.
Basically I want to take an image that the user chooses from their photo library and then apply a watermark, a triangle in the lower right that has the app name on it. I have the second image already made with a transparent layer in photoshop.
我尝试了一个函数，我不记得确切的名称，但它涉及 CGIImages 和掩码.这结合了两个图像，但是作为一个遮罩，这使得透明层所在的图像更暗，图像本身并没有合并，只是被遮罩了.
I tried a function, which I can't remember the exact name, but it involved CGIImages and masks. This combines the two images, but as a mask, which made the image darker where the transparent layer was and the images were not merged per se, just masked.
如何让水印图像与另一个图像合并，制作 UIImage，而不在屏幕上显示图像?
How would I get the watermark image to merge with another image, to make a UIImage, without displaying the images on the screen?
谢谢.
正确答案
很简单:
UIImage *backgroundImage = [UIImage imageNamed:@"image.png"];
UIImage *watermarkImage = [UIImage imageNamed:@"watermark.png"];
UIGraphicsBeginImageContext(backgroundImage.size);
[backgroundImage drawInRect:CGRectMake(0, 0, backgroundImage.size.width, backgroundImage.size.height)];
[watermarkImage drawInRect:CGRectMake(backgroundImage.size.width - watermarkImage.size.width, backgroundImage.size.height - watermarkImage.size.height, watermarkImage.size.width, watermarkImage.size.height)];
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
如果您希望背景和水印大小相同，请使用此代码
If you want the background and watermark to be of the same size then use this code
...
[backgroundImage drawInRect:CGRectMake(0, 0, backgroundImage.size.width, backgroundImage.size.height)];
[watermarkImage drawInRect:CGRectMake(0, 0, backgroundImage.size.width, backgroundImage.size.height)];
...
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