iOS UIImage 如何以编程方式将黑色转换为透明？

Question

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Answer 1

您可以使用 Core Image Filters - 特别是过滤器 CIMaskToAlpha

有关使用 CIFilters 的详细说明，请访问 Apple's Core Image Programming Guide和一个 RayWenderlich tutorial

编辑:此滤镜采用黑色像素并使它们完全透明，并将白色像素替换为不透明像素、将灰色像素替换为部分透明像素等。

-(void)setImage:(UIImage *)image_
{

    UIImage *entryImage  = image_;
    CIContext *context = [CIContext contextWithOptions:nil];

    CIImage *image = [CIImage imageWithCGImage:[entryImage CGImage]];
    CIFilter *filter = [CIFilter filterWithName:@"CIMaskToAlpha"];
    [filter setDefaults];
    [filter setValue:image forKey:kCIInputImageKey];
    //    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CIImage *result = [filter outputImage];

    CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];

    UIImage *newImage = [UIImage imageWithCGImage:cgImage scale:[entryImage scale] orientation:UIImageOrientationUp];
    CGImageRelease(cgImage);
    [super setImage:newImage];
}