UIImage 替换为另一个不平滑的 UIImage

Posted 2023-02-23

【中文标题】UIImage 替换为另一个不平滑的 UIImage

【英文标题】：UIImage replaces with another UIImage not Smooth

【发布时间】：2014-03-25 08:44:46

【问题描述】：

我正在做一个项目，我正在从UIWebView 渲染Images，然后使用自定义UITableViewCell 显示为tableView。当UITableView 第一次出现时...没有要显示的渲染图像，所以我在单元格中显示默认图像（即icon-thumb.png）。图像渲染后，我将重新加载 UITableView。 我这样做如下......

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

        NSString *reuseIdentifier = @"CustomTableViewID";             CustomTableViewCell  *cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier];
        if (cell == nil)
        
            cell = (CustomTableViewCell *)[[[NSBundle mainBundle] loadNibNamed:@"CustomTableViewCell" owner:nil options:nil] objectAtIndex:0];
        

        CGRect mainImageViewFrame = CGRectMake(9, 31, 202, 171);
        cell.mainImageView.frame = mainImageViewFrame;

        [cell setBackgroundColor:[UIColor clearColor]];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
        cell.transform = CGAffineTransformMakeRotation(M_PI * 0.5);

        cell.slideNumberLbl.textColor = [UIColor whiteColor];
        cell.slideNumberLbl.backgroundColor = [UIColor grayColor];
        cell.slideNumberLbl.layer.cornerRadius = 5.0;
        cell.slideNumberLbl.alpha = 0.5;
        [cell.slideNumberLbl setTextAlignment:NSTextAlignmentCenter];
        cell.slideNumberLbl.text = [NSString stringWithFormat:@"%d",indexPath.row+1];

        [cell.mainImageView setBackgroundColor:[UIColor clearColor]];

        [cell.reflectionImageView setContentMode:UIViewContentModeScaleToFill];
        cell.reflectionImageView.alpha = 0.15;

        NSFileManager *manager = [NSFileManager defaultManager];
        NSString *thumbImagepath = [self.storageDirPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%d_thumb%@",indexPath.row, Image_Extension_JPG]];

        if([manager fileExistsAtPath:thumbImagepath])
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^
                __block UIImage *img = [UIImage imageWithContentsOfFile:thumbImagepath];
                dispatch_async(dispatch_get_main_queue(), ^

                    CGRect mainImageViewFrame = CGRectMake(9, 31, 202, 171);
                    cell.mainImageView.frame = mainImageViewFrame;
                    cell.mainImageView.image = img;
                    [cell.mainImageView setContentMode:UIViewContentModeScaleAspectFit];
                    img = nil;
                    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^
                        __block UIImage *reflectionImg = [self reflectedImage:cell.mainImageView withHeight:cell.mainImageView.frame.size.height];
                        dispatch_async(dispatch_get_main_queue(), ^
                            cell.reflectionImageView.image = reflectionImg;
                            reflectionImg = nil;
                        );
                    );
                );
            );
        
        else
            CGRect mainImageViewFrame = CGRectMake(9, 31, 202, 171);
            mainImageViewFrame.origin.y = mainImageViewFrame.origin.y+10;
            mainImageViewFrame.size.height = mainImageViewFrame.size.height-20;
            cell.mainImageView.frame = mainImageViewFrame;

            [cell.mainImageView setContentMode:UIViewContentModeCenter];
            [cell.mainImageView setBackgroundColor:[UIColor whiteColor]];
            cell.mainImageView.image = [UIImage imageNamed:@"icon-thumb.png"];
            [cell.reflectionImageView setBackgroundColor:[UIColor whiteColor]];
            [cell.reflectionImageView setImage:[UIImage imageNamed:@"reflection_temp.png"]];
        

        return cell;
    

问题是，当真实图像渲染完成后，默认图像（即 icon-thumb.png）被真实图像替换..替换不流畅，图像替换为 flash/或全部突然，但它需要非常顺利...任何建议，提前谢谢。

【问题讨论】：

***.com/questions/7638831/…

【参考方案1】：

你可以使用 CATransition 例如

 CATransition *transition = [CATransition animation];
    transition.duration = 0.2;//duration
    transition.type = kCATransitionFade; //choose your animation
    [yourCell.layer addAnimation:transition forKey:nil];
    [yourCell.mainimageview setImage:img];

【讨论】：

savana 感谢您的回复，但我已经解决了问题。我找到了***.com/questions/2834573/…。但你的回答我也会接受，因为这也可以。

【参考方案2】：

这可能是愚蠢的答案，但您没有尝试为此使用动画吗？

像这样：

        [UIView animateWithDuration:duration animations:^
             completion:^(BOOL finished) 
            
        ];

【参考方案3】：

我会做如下的事情：

[UIView transitionWithView:cell.mainImageView
                  duration:0.2f
                   options:UIViewAnimationOptionTransitionCrossDissolve
                animations:^
                    cell.mainImageView.image = [UIImage imageNamed:@"icon-thumb.png"];
                 completion:nil];

我发现这种方法稍微优雅一些​​。