UITableViewCell中的图像模糊时的性能问题 [英] Performance Issue while blurring image in UITableViewCell

问题描述

我的自定义UITableViewCell中有一个UIImageView.包含的图像应模糊.我知道UIVisualEffectsView，但是首先，这在iOS8之前是不可用的，其次，对于我的用例而言，模糊有些沉重.

I got an UIImageView in my custom UITableViewCell. The included image should be blurred. I am aware of UIVisualEffectsView but first of all this is not available prior iOS8 and second the blur is a bit to heavy for my use case.

这就是为什么我想出这个解决方案的原因:

Thats why I came up with this solution:

cellForRowAtIndexPath示例:

- (UITableViewCell *)tableView:(UITableView *)tableView
         cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"showCell";

    DEShowCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

    if (cell == nil)
    {
        [tableView registerNib:[UINib nibWithNibName:@"DEShowCell" bundle:[NSBundle mainBundle]] forCellReuseIdentifier:cellIdentifier];
        cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    }

    [cell setBackgroundImageWithBlur:[UIImage imageNamed:@"sampleBanner"]];

    return cell;
}

我的自定义单元格:

-(void)setBackgroundImageWithBlur:(UIImage *)image {
    [self.backgroundImageView setImage:[self blurWithCoreImage:image]];
}

- (UIImage *)blurWithCoreImage:(UIImage *)sourceImage
{
    CIImage *inputImage = [CIImage imageWithCGImage:sourceImage.CGImage];

    // Apply Affine-Clamp filter to stretch the image so that it does not
    // look shrunken when gaussian blur is applied
    CGAffineTransform transform = CGAffineTransformIdentity;
    CIFilter *clampFilter = [CIFilter filterWithName:@"CIAffineClamp"];
    [clampFilter setValue:inputImage forKey:@"inputImage"];
    [clampFilter setValue:[NSValue valueWithBytes:&transform objCType:@encode(CGAffineTransform)] forKey:@"inputTransform"];

    // Apply gaussian blur filter with radius of 30
    CIFilter *gaussianBlurFilter = [CIFilter filterWithName: @"CIGaussianBlur"];
    [gaussianBlurFilter setValue:clampFilter.outputImage forKey: @"inputImage"];
    [gaussianBlurFilter setValue:@10 forKey:@"inputRadius"];

    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef cgImage = [context createCGImage:gaussianBlurFilter.outputImage fromRect:[inputImage extent]];

    // Set up output context.
    UIGraphicsBeginImageContext(self.frame.size);
    CGContextRef outputContext = UIGraphicsGetCurrentContext();

    // Invert image coordinates
    CGContextScaleCTM(outputContext, 1.0, -1.0);
    CGContextTranslateCTM(outputContext, 0, -self.frame.size.height);

    // Draw base image.
    CGContextDrawImage(outputContext, self.frame, cgImage);

    // Apply white tint
    CGContextSaveGState(outputContext);
    CGContextSetFillColorWithColor(outputContext, [UIColor colorWithWhite:1 alpha:0.2].CGColor);
    CGContextFillRect(outputContext, self.frame);
    CGContextRestoreGState(outputContext);

    // Output image is ready.
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return outputImage;
}

不幸的是，当我尝试滚动UITableView时，这给我带来了巨大的性能问题.

Unfortunately this gives me huge performance issues when I try to scroll the UITableView.

所以我问我如何解决?我可以使用某些库来进行像GPUImage这样的模糊处理，我想它会更快，但是我不知道这是否可以带来很大的不同.

So I asked me how to workaround ? I could use some library to do the blurring like GPUImage which will be faster I guess, but I don't know if this can make a big difference.

我认为UITableView将包含大约 20-60行.

还有其他诸如缓存之类的想法吗?

Any other ideas like caching or something else ?

推荐答案

我将在设置中使用 FXBlurView 动态= NO.它具有不错的性能.

I will use FXBlurView with setting dynamic = NO. It has decent performance.

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