我正在创建一个基于视频的应用程序，我必须从本地图库中选择任何视频，并且必须使用 CATextLayer 在视频上添加文本。为此，我使用以下代码：
- (void) createWatermark:(UIImage*)image video:(NSURL*)videoURL
{
if (videoURL == nil)
return;
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:videoURL options:nil];
AVMutableComposition* mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack* compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack* clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:clipVideoTrack
atTime:kCMTimeZero error:nil];
[compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];
// create the layer with the watermark image
CALayer* aLayer = [CALayer layer];
aLayer.contents = (id)image.CGImage;
aLayer.frame = CGRectMake(50, 100, image.size.width, image.size.height);
aLayer.opacity = 0.9;
//sorts the layer in proper order
AVAssetTrack* videoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
CGSize videoSize = [videoTrack naturalSize];
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
videoLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:aLayer];
// create text Layer
CATextLayer* titleLayer = [CATextLayer layer];
titleLayer.backgroundColor = [UIColor clearColor].CGColor;
titleLayer.string = @"Dummy text";
titleLayer.font = CFBridgingRetain(@"Helvetica");
titleLayer.fontSize = 28;
titleLayer.shadowOpacity = 0.5;
titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.frame = CGRectMake(0, 50, videoSize.width, videoSize.height / 6);
[parentLayer addSublayer:titleLayer];
//create the composition and add the instructions to insert the layer:
AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition];
videoComp.renderSize = videoSize;
videoComp.frameDuration = CMTimeMake(1, 30);
videoComp.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
/// instruction
AVMutableVideoCompositionInstruction* instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mixComposition duration]);
AVAssetTrack* mixVideoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:mixVideoTrack];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
videoComp.instructions = [NSArray arrayWithObject: instruction];
// export video
_assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
_assetExport.videoComposition = videoComp;
NSLog (@"created exporter. supportedFileTypes: %@", _assetExport.supportedFileTypes);
NSString* videoName = @"NewWatermarkedVideo.mov";
NSString* exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:videoName];
NSURL* exportUrl = [NSURL fileURLWithPath:exportPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath])
[[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
_assetExport.outputFileType = AVFileTypeQuickTimeMovie;
_assetExport.outputURL = exportUrl;
_assetExport.shouldOptimizeForNetworkUse = YES;
[_assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
//Final code here
switch (_assetExport.status)
{
case AVAssetExportSessionStatusUnknown:
NSLog(@"Unknown");
break;
case AVAssetExportSessionStatusWaiting:
NSLog(@"Waiting");
break;
case AVAssetExportSessionStatusExporting:
NSLog(@"Exporting");
break;
case AVAssetExportSessionStatusCompleted:
NSLog(@"Created new water mark image");
_playButton.hidden = NO;
break;
case AVAssetExportSessionStatusFailed:
NSLog(@"Failed- %@", _assetExport.error);
break;
case AVAssetExportSessionStatusCancelled:
NSLog(@"Cancelled");
break;
}
}
];
}
使用上面的代码，我可以在我的视频上设置文本。但现在我必须在 CATextLayer 上提供淡入/淡出动画或在视频上显示移动文本。请建议我。提前致谢！
尝试使用核心动画框架中声明的 CAKeyframeAnimation 类。
例如：
//start from zero opacity
titleLayer.opacity = 0;
CAKeyframeAnimation *fadeInAndOut = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];
fadeInAndOut.duration = 5.0; //5 seconds will be your fade in fade out animation.
fadeInAndOut.autoreverses = NO;
// from 0.0 * animDuration time to 0.2 * animDuration time your animation will animate opacity from zero to 1.0.
// from 0.2 * animDuration time to 0.8 * animDuration time your opacity will be 1.0
// from 0.8 * animDuration time to 1.0 * animDuration time your animation will animate opacity from 1.0 opacity to zero.
fadeInAndOut.keyTimes = @[@(0.0), @(0.2), @(0.8), @(1.0)];
fadeInAndOut.values = @[@(0.0), @(1.0), @(1.0), @(0.0)];
fadeInAndOut.beginTime = 1.0;
fadeInAndOut.removedOnCompletion = NO;
fadeInAndOut.fillMode = kCAFillModeBoth;
[titleLayer addAnimation:fadeInAndOut forKey:nil];
我希望您能清楚地了解这一点。使用相同的方式您可以为标签位置设置动画。
更新
对于动画位置试试这个
CAKeyframeAnimation *fadeInAndOut = [CAKeyframeAnimation animationWithKeyPath:@"position"];
fadeInAndOut.duration = 5.0;
fadeInAndOut.autoreverses = NO;
fadeInAndOut.keyTimes = @[@(0.0), @(0.2), @(0.8), @(1.0)];
fadeInAndOut.values = @[[NSValue valueWithCGPoint:CGPointMake(20, 40)],
[NSValue valueWithCGPoint:CGPointMake(200, 40)],
[NSValue valueWithCGPoint:CGPointMake(200, 40)],
[NSValue valueWithCGPoint:CGPointMake(400, 40)]];
fadeInAndOut.beginTime = 1.0;
fadeInAndOut.removedOnCompletion = NO;
fadeInAndOut.fillMode = kCAFillModeBoth;
[titleLayer addAnimation:fadeInAndOut forKey:nil];
出于解释目的，我对点进行了硬编码。您可以自己计算点和动画持续时间。
首先添加父图层：
let parentLayer = CALayer()
之后添加叠加层以添加淡入淡出动画：
let overlayLayer = CALayer()
以及用于添加淡入淡出动画的附加电话信息：
overlayLayer.addFadeAnimationWithTime(showTime: startTime, endTime: endTime)
并将其添加到父层：
parentLayer.addSublayer(overlayLayer)
带有 startTime 和 endTime 的淡入淡出动画扩展：
extension CALayer {
func addFadeAnimationWithTime(showTime:CGFloat, endTime:CGFloat) {
let fadeInAnimation = CABasicAnimation.init(keyPath: "opacity")
fadeInAnimation.duration = 1
fadeInAnimation.fromValue = NSNumber(value: 0)
fadeInAnimation.toValue = NSNumber(value: 1)
fadeInAnimation.isRemovedOnCompletion = false
fadeInAnimation.beginTime = CFTimeInterval(showTime)
fadeInAnimation.fillMode = CAMediaTimingFillMode.backwards
self.add(fadeInAnimation, forKey: "fadeIn")
if endTime > 0 {
let fadeOutAnimation = CABasicAnimation.init(keyPath: "opacity")
fadeOutAnimation.duration = 1
fadeOutAnimation.fromValue = NSNumber(value: 1)
fadeOutAnimation.toValue = NSNumber(value: 0)
fadeOutAnimation.isRemovedOnCompletion = false
fadeOutAnimation.beginTime = CFTimeInterval(endTime)
fadeOutAnimation.fillMode = CAMediaTimingFillMode.forwards
self.add(fadeOutAnimation, forKey: "fadeOut")
}
}
}
private func showLayer(_ layer: CALayer, on superLayer: CALayer, from: CGFloat, to: CGFloat) {
superLayer.addSublayer(layer)
showLayer(layer, at: from)
hideLayer(layer, at: to)
}
private func showLayer(_ layer: CALayer, at time: CGFloat) {
if layer.opacity != 0 {
layer.opacity = 0
}
let appearAnimation = CABasicAnimation(keyPath: "opacity")
let duration = 0.0001
appearAnimation.beginTime = Double(time)-duration
appearAnimation.duration = duration
appearAnimation.fromValue = 0
appearAnimation.toValue = 1
appearAnimation.fillMode = .forwards
appearAnimation.isRemovedOnCompletion = false
layer.add(appearAnimation, forKey: nil)
}
private func hideLayer(_ layer: CALayer, at time: CGFloat) {
let disappearAnimation = CABasicAnimation(keyPath: "opacity")
let duration = 0.0001
disappearAnimation.beginTime = CFTimeInterval(time)
disappearAnimation.duration = duration
disappearAnimation.fromValue = 1
disappearAnimation.toValue = 0
disappearAnimation.fillMode = .forwards
disappearAnimation.isRemovedOnCompletion = false
layer.add(disappearAnimation, forKey: nil)
}