UIGraphicsBeginImageContext创建的图像永远保留在内存中 [英] UIGraphicsBeginImageContext created image stays in memory forever

问题描述

我正在使用Core Graphics创建图像的许多颜色变化。我总共需要创建约320个，但是逐渐地，该应用的内存使用量一直在增加，直到崩溃为止。从仪器，我看到更多的CGImage对象正在创建并保持活动状态。我想发布它们，因为我将图像以PNG格式存储到缓存目录中。

I'm creating many colour variations of an image using Core Graphics. I need to create about 320 in total but gradually, the memory usage of the app keeps increasing until it crashes. From Instruments, I see that more CGImage objects are being created and stay alive. I want to release them because I store the images to the cache directory in PNG format.

我搜索了所有我找不到的成功解决方案。任何帮助表示赞赏。谢谢。

I have searched through all other solutions I could find without success. Any help is appreciated. Thanks.

这是主要部分：

+(UIImage *)tintedImageFromImage:(UIImage *)sourceImage colour:(UIColor *)color intensity:(float)intensity {

    if (UIGraphicsBeginImageContextWithOptions != NULL) {

        UIGraphicsBeginImageContextWithOptions(sourceImage.size, NO, 0.0);

    } else {

        UIGraphicsBeginImageContext(sourceImage.size);
    }

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, sourceImage.size.width, sourceImage.size.height);

    // draw alpha-mask
    CGContextSetBlendMode(context, kCGBlendModeNormal);
    CGContextDrawImage(context, rect, sourceImage.CGImage);

    // draw tint color, preserving alpha values of original image
    CGContextSetBlendMode(context, kCGBlendModeSourceIn);
    [color setFill];
    CGContextFillRect(context, rect);


    //Set the original greyscale template as the overlay of the new image
    sourceImage = [self verticallyFlipImage:sourceImage];
    [sourceImage drawInRect:CGRectMake(0,0, sourceImage.size.width,sourceImage.size.height) blendMode:kCGBlendModeMultiply alpha:intensity];

    UIImage *colouredImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    colouredImage = [self verticallyFlipImage:colouredImage];


    return colouredImage;
}

这用于翻转图像：

+(UIImage *)verticallyFlipImage:(UIImage *)originalImage {

    UIImageView *tempImageView = [[UIImageView alloc] initWithImage:originalImage];

    UIGraphicsBeginImageContext(tempImageView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, tempImageView.frame.size.height);

    CGContextConcatCTM(context, flipVertical);

    [tempImageView.layer renderInContext:context];

    UIImage *flippedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return flippedImage;
}

推荐答案

添加到 verticallyFlipImage 行 tempImageView.image = nil; 以便使图像视图释放图像。这样可以解决问题。

Add to verticallyFlipImage the line tempImageView.image = nil; in order to make the image view release the image. This solves the problem.

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