如何将UIImage中的颜色“白色”更改为透明 [英] How can I change the color 'white' from a UIImage to transparent

问题描述

我有一个UIImage作为截图生成。我正在使用以下代码添加此对象：

I've got a UIImage which is generated as a screenshot. I'm adding this object with the following code:

self.view.backgroundColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:0.0];
    drawImage.backgroundColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:0.0];

    UIGraphicsBeginImageContext(self.view.bounds.size);
    [drawImage.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    CGImageRef rawImageRef=viewImage.CGImage;
    const float colorMasking[6] = {255,255,255,255,0,0}; 
    CGImageCreateWithMaskingColors(rawImageRef, colorMasking);
    UIImage *newImage = [UIImage imageWithCGImage:rawImageRef];

然而我的图像只变白了，我想让图像透明使用CGImageCreateMaskingColors它是白色的地方。

However my Image only turns white, and I'd like to have the image to be transparent on the places where it's white by using CGImageCreateMaskingColors.

希望有人可以帮助我。

推荐答案

UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, YES, 1.0);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

CGImageRef rawImageRef = viewImage.CGImage;
const float colorMasking[6] = {255, 255, 255, 255, 255, 255};
UIGraphicsBeginImageContext(viewImage.size);
CGImageRef maskedImageRef = CGImageCreateWithMaskingColors(rawImageRef, colorMasking);
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), 0.0, viewImage.size.height);
CGContextScaleCTM(UIGraphicsGetCurrentContext(), 1.0, -1.0);

CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, viewImage.size.width, viewImage.size.height), maskedImageRef);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
CGImageRelease(maskedImageRef);
UIGraphicsEndImageContext();

这篇关于如何将UIImage中的颜色“白色”更改为透明的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！