如何缩放视频以匹配渲染大小

Question

我正在创建一个渲染为

的视频

我正在使用以下代码旋转和缩放肖像视频以适合框架的高度。理想情况下，它也应该位于中心。我对缩放如何使其适应变得有些困惑。到目前为止，无论我尝试什么，它似乎太大了。

框架尺寸应为

  

AVAssetExportPreset1920x1080

CGFloat FirstAssetScaleToFitRatio = 1920/1080;
            if(isFirstAssetPortrait_){
                FirstAssetScaleToFitRatio = 2/2;
                CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
                [rotator setTransform:CGAffineTransformConcat(videoAssetTrack.preferredTransform, FirstAssetScaleFactor) atTime:kCMTimeZero];
            }else{
                CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
                [rotator setTransform:CGAffineTransformConcat(CGAffineTransformConcat(videoAssetTrack.preferredTransform, FirstAssetScaleFactor),CGAffineTransformMakeTranslation(0, 0)) atTime:kCMTimeZero];
            }