iPhone中UIImage的内存分配和发布？

Question

我在iPhone中使用以下代码来获得较小的裁剪图像,如下所示:

- (UIImage*) getSmallImage:(UIImage*) img
{
    CGSize size = img.size;
    CGFloat ratio = 0;
    if (size.width < size.height) {
        ratio = 36 / size.width;
    } else {
        ratio = 36 / size.height;
    }
    CGRect rect = CGRectMake(0.0, 0.0, ratio * size.width, ratio * size.height);

    UIGraphicsBeginImageContext(rect.size);
    [img drawInRect:rect];

    UIImage *tempImg = [UIGraphicsGetImageFromCurrentImageContext() retain];

    UIGraphicsEndImageContext();
    return [tempImg autorelease];
}

- (UIImage*)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect
{

    //create a context to do our clipping in
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    //create a rect with the size we want to crop the image to
    //the X and Y here are zero so we start at the beginning of our
    //newly created context

    CGFloat X = (imageToCrop.size.width - rect.size.width)/2;
    CGFloat Y = (imageToCrop.size.height - rect.size.height)/2;


    CGRect clippedRect = CGRectMake(X, Y, rect.size.width, rect.size.height);
    //CGContextClipToRect( currentContext, clippedRect);



    //create a rect equivalent to the full size of the image
    //offset the rect by the X and Y we want to start the crop
    //from in order to cut off anything before them
    CGRect drawRect = CGRectMake(0,
                                 0,
                                 imageToCrop.size.width,
                                 imageToCrop.size.height);

    CGContextTranslateCTM(currentContext, 0.0, drawRect.size.height);
    CGContextScaleCTM(currentContext, 1.0, -1.0);
    //draw the image to our clipped context using our offset rect
    //CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage);


    CGImageRef tmp = CGImageCreateWithImageInRect(imageToCrop.CGImage, clippedRect);

    //pull the image from our cropped context
    UIImage *cropped = [UIImage imageWithCGImage:tmp];//UIGraphicsGetImageFromCurrentImageContext();
    CGImageRelease(tmp);
    //pop the context to get back to the default
    UIGraphicsEndImageContext();

    //Note: this is autoreleased*/
    return cropped;
}

我在cellForRowAtIndexPath中使用以下代码行来更新单元格的图像:

cell.img.image = [self imageByCropping:[self getSmallImage:[UIImage imageNamed:@"goal_image.png"]] toRect:CGRectMake(0, 0, 36, 36)];

现在当我添加这个表视图并从导航控制器弹出它时,我看到了一个内存加息.我看到没有泄漏,但内存不断攀升.

请注意,每行的图像都会发生变化,我正在使用延迟初始化创建控制器,这是我创建或在需要时分配它.

我在互联网上看到许多人面临同样的问题,但非常罕见的好解决方案.我有多个视图使用相同的方式,我看到几乎内存在20-25视图转换中提升到4MB.

解决此问题的好方法是什么？

TNX.

Answer 1

在 EndImageContext 之前，您无法从例程返回：

return UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

尝试这个：

UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;

您不需要注释掉的保留或自动释放。