调整uiimage大小时内存使用率高

Question

在矩形中调整和绘制 UIImage 时会占用大量内存。

   - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
    {
        UIImage *selectedImage=[info objectForKey:UIImagePickerControllerOriginalImage];

        //  COMPRESSING IMAGE
     NSData   *selectedImageData=UIImageJPEGRepresentation(selectedImage, 0.5);
        UIImage *selectedImageFromData=[UIImage imageWithData:selectedImageData];


        //SCALING UIIMAGE
        UIImage *scaledImage=[[UIImage alloc]init];
        if (((selectedImageFromData.size.width>3264) && (selectedImageFromData.size.height>2448)) || ((selectedImageFromData.size.height>3264) && (selectedImageFromData.size.width>2448)))
        {
           CGFloat originalWidth=selectedImageFromData.size.width;
                CGFloat originalHeight=selectedImageFromData.size.height;
                CGFloat myWidth=2048;
                CGFloat widthRatio=myWidth/originalWidth;
                CGFloat dynamicHeight=widthRatio*originalHeight;

         CGImageRef CoreGraphicsImage=selectedImageFromData.CGImage;
        CGColorSpaceRef colorSpace = CGImageGetColorSpace(CoreGraphicsImage);
        CGBitmapInfo bitmapInfo=CGImageGetBitmapInfo(CoreGraphicsImage);
  CGImageGetBitsPerComponent(CoreGraphicsImage);

        CGContextRef context=CGBitmapContextCreate(NULL, myWidth, dynamicHeight, CGImageGetBitsPerComponent(CoreGraphicsImage), CGImageGetBytesPerRow(CoreGraphicsImage), colorSpace, bitmapInfo);


        CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
        CGContextDrawImage(context, CGRectMake(0, 0, myWidth, dynamicHeight), CoreGraphicsImage);
        CGImageRef CGscaledImage=CGBitmapContextCreateImage(context);
        UIImage *CGLastimage = [UIImage imageWithCGImage: CGscaledImage];


        NSLog(@"%f",CGLastimage.size.width);
        NSLog(@"%f",CGLastimage.size.height);

        VisualEffectImageVIew.image=CGLastimage;
                BackgroundImageView.image=CGLastimage;
                ForegroundImageView.image=CGLastimage;
        }
        else
        {
            NSLog(@" HEIGHT %f",selectedImageFromData.size.height);
            NSLog(@" WIDTH %f",selectedImageFromData.size.width);

        VisualEffectImageVIew.image=selectedImageFromData;
        BackgroundImageView.image=selectedImageFromData;
        ForegroundImageView.image=selectedImageFromData;
        }
       if(UI_USER_INTERFACE_IDIOM()==UIUserInterfaceIdiomPhone)
        {
            [picker dismissViewControllerAnimated:YES completion:nil];
        }
        else
        {


            [popoverController dismissPopoverAnimated:YES];

            [self popoverControllerDidDismissPopover:popoverController];
      }

    }

这是下面的图片，在图片中你可以看到上面提到的代码使用了太多的内存。想知道为什么它使用了太多内存，并希望有任何解决方案。

Answer 1

在图像方面，我一直是Brad Larson's GPUImage 的忠实粉丝，它可以做任何你想做的事情，并且使用 GPU 而不是 CPU，这让你有足够的能力来避免由于内存压力而导致的崩溃。

而且还不错。

This stackoverflow question 还可以帮助您在完成项目设置后实现您想要的。

希望这会有所帮助:)

Answer 2

您使用 CPU 将数据绘制到帧中，我建议您使用 CGImage 在 GPU 上下文中进行绘制

- (UIImage *) scaleToSize: (CGSize)size
{
    // Scalling selected image to targeted size
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, size.width, size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
    CGContextClearRect(context, CGRectMake(0, 0, size.width, size.height));

    if(self.imageOrientation == UIImageOrientationRight)
    {
        CGContextRotateCTM(context, -M_PI_2);
        CGContextTranslateCTM(context, -size.height, 0.0f);
        CGContextDrawImage(context, CGRectMake(0, 0, size.height, size.width), self.CGImage);
    }
    else
        CGContextDrawImage(context, CGRectMake(0, 0, size.width, size.height), self.CGImage);

    CGImageRef scaledImage=CGBitmapContextCreateImage(context);

    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);

    UIImage *image = [UIImage imageWithCGImage: scaledImage];

    CGImageRelease(scaledImage);

    return image;
}