项目有一个新需求.需要选取一段视中的一段生成GIF图.整个过程中踩了不少坑,在此贴出来给需要的朋友
寻找方案当初借鉴了他人代码,但是忘记来源.如果有异议请随时联系保证第一时间删除
首先核心类是AVKit中的AVAsset和AVAssetImageGenerator.
AVAsset是苹果在iOS4.0-10.0中的音视频框架中的对象类,从相册中取出的对象就是AVAsset.
AVAssetImageGenerator是一个可以从AVAsset中获取某一个时间点的一张图的类.
AVKit框架在8.0后更新为了Photos框架.但是相关代码未找到.估未更新.
文章最下方会贴完整代码
核心思想:创建一个集合,其中包含了N个帧所在时间段的对象,然后循环集合,取出每个对象.根据对象所在的时间生成图片,将所有图片拼接为一个GIF图->生成本地GIF文件
处理帧对象方法
- (void)createGIFfromURL:(NSURL*)videoURL loopCount:(int)loopCount startSecond:(float)fltStartSecond delayTime:(CGFloat)delayTime gifTime:(float)fltGifTime gifImagePath:(NSString *)imagePath{
NSDictionary *fileProperties = [self filePropertiesWithLoopCount:loopCount]; NSDictionary *frameProperties = [self framePropertiesWithDelayTime:delayTime];
AVURLAsset *asset = [AVURLAsset assetWithURL:videoURL];
float videoWidth = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width; float videoHeight = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height;
GIFSize optimalSize = GIFSizeMedium; if (videoWidth >= 1200 || videoHeight >= 1200)
optimalSize = GIFSizeVeryLow; else if (videoWidth >= 800 || videoHeight >= 800)
optimalSize = GIFSizeLow; else if (videoWidth >= 400 || videoHeight >= 400)
optimalSize = GIFSizeMedium; else if (videoWidth < 400|| videoHeight < 400)
optimalSize = GIFSizeHigh;
int frameCount = fltGifTime * kFrameInSecond;
//两帧的时间间隔
float increment = (float)fltGifTime/frameCount;
// Add frames to the buffer
NSMutableArray *timePoints = [NSMutableArray array]; for (int currentFrame = 0; currentFrame<frameCount; ++currentFrame) { float seconds = fltStartSecond + (float)increment * currentFrame; CMTime time = CMTimeMakeWithSeconds(seconds, 1 *NSEC_PER_SEC);
[timePoints addObject:[NSValue valueWithCMTime:time]];
}
[self createGIFforTimePoints:timePoints fromURL:videoURL fileProperties:fileProperties frameProperties:frameProperties gifImagePath:imagePath frameCount:frameCount gifSize:optimalSize];
}方法的核心是生成多个关键帧的时间并添加进一个数组.供后续生成图片使用
- (NSURL *)createGIFforTimePoints:(NSArray *)timePoints fromURL:(NSURL *)url fileProperties:(NSDictionary *)fileProperties frameProperties:(NSDictionary *)frameProperties gifImagePath:(NSString *)imagePath frameCount:(int)frameCount gifSize:(GIFSize)gifSize{
NSURL *fileURL = [NSURL fileURLWithPath:imagePath]; if (fileURL == nil) return nil;
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)fileURL, kUTTypeGIF , frameCount, NULL); CGImageDestinationSetProperties(destination, (CFDictionaryRef)fileProperties);
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:nil]; AVAssetImageGenerator *generator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
generator.appliesPreferredTrackTransform = YES;
generator.requestedTimeToleranceBefore = kCMTimeZero;
generator.requestedTimeToleranceAfter = kCMTimeZero;
NSError *error = nil; CGImageRef previousImageRefCopy = nil; CGImageRef imageRef; NSLog(@"starat");
for (NSValue *time in timePoints) {
imageRef = [generator copyCGImageAtTime:[time CMTimeValue] actualTime:nil error:&error]; if((float)gifSize/10 != 1){
imageRef = createImageWithScale(imageRef, (float)gifSize/10);
}
if (error) {
_error =error; NSLog(@"Error copying image: %@", error); return nil;
} if (imageRef) { CGImageRelease(previousImageRefCopy);
previousImageRefCopy = CGImageCreateCopy(imageRef);
} else if (previousImageRefCopy) {
imageRef = CGImageCreateCopy(previousImageRefCopy);
} else {
_error =[NSError errorWithDomain:NSStringFromClass([self class]) code:0 userInfo:@{NSLocalizedDescriptionKey:@"Error copying image and no previous frames to duplicate"}]; NSLog(@"Error copying image and no previous frames to duplicate"); return nil;
} CGImageDestinationAddImage(destination, imageRef, (CFDictionaryRef)frameProperties); CGImageRelease(imageRef);
} NSLog(@"end"); CGImageRelease(previousImageRefCopy);
// Finalize the GIF
if (!CGImageDestinationFinalize(destination)) {
_error =error;
NSLog(@"Failed to finalize GIF destination: %@", error); if (destination != nil) { CFRelease(destination);
} return nil;
} CFRelease(destination);
return fileURL;
}根据每一帧所在的时间去生成图片.组合成一个GIF.
总体功能是实现了.但是效率有些低下.24帧/s的一个GIF 3s生成需要大概20s.所有这块儿还是需要进行优化的
//// GIFGenerator.m// GIFGenerator//// Created by 侯志桐Work on 2018/7/19.// Copyright © 2018年 BlackMonkey. All rights reserved.//#import "GIFGenerator.h"#import <AVKit/AVKit.h>#import <MobileCoreServices/UTCoreTypes.h>//typedef NS_ENUM(NSInteger, GIFSize) { GIFSizeVeryLow = 2, GIFSizeLow = 3, GIFSizeMedium = 5, GIFSizeHigh = 7, GIFSizeOriginal = 10 };typedef NS_ENUM(NSInteger, GIFSize) { GIFSizeVeryLow = 1, GIFSizeLow = 2, GIFSizeMedium = 3, GIFSizeHigh = 5, GIFSizeOriginal = 10 };//动画1s多少帧#define kFrameInSecond (24)@interface GIFGenerator()@property (nonatomic,strong)NSError *error;@end@implementation GIFGenerator+(instancetype)shareGIFGenerator{ static GIFGenerator *generator; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{
generator = [[self alloc] init];
}); return generator;
}
- (void)generatorGIFWithLocalVideoPath:(NSString *)strVideoPath startSecond:(float)startSecond gifTime:(float)gifTime gifFilePath:(NSString *)gifFilePath completeBlock:(void(^)(BOOL isSuccess,NSError *error))completeBlock{ self.error = nil; if(![[NSFileManager defaultManager] fileExistsAtPath:strVideoPath]){ if(completeBlock){
completeBlock(NO,[[NSError alloc] initWithDomain:NSURLErrorDomain code:-1 userInfo:@{@"msg":@"文件不存在"}]);
} return;
} dispatch_async(dispatch_get_global_queue(0, 0), ^{ NSURL *videoUrl = [NSURL fileURLWithPath:strVideoPath]; CGFloat delayTime = 1.f / kFrameInSecond;
[self createGIFfromURL:videoUrl loopCount:1 startSecond:startSecond delayTime:delayTime gifTime:gifTime gifImagePath:gifFilePath];
if(completeBlock){ dispatch_async(dispatch_get_main_queue(), ^{
completeBlock(!self.error,self.error);
});
}
});
}
- (void)createGIFfromURL:(NSURL*)videoURL loopCount:(int)loopCount startSecond:(float)fltStartSecond delayTime:(CGFloat)delayTime gifTime:(float)fltGifTime gifImagePath:(NSString *)imagePath{
NSDictionary *fileProperties = [self filePropertiesWithLoopCount:loopCount]; NSDictionary *frameProperties = [self framePropertiesWithDelayTime:delayTime];
AVURLAsset *asset = [AVURLAsset assetWithURL:videoURL];
float videoWidth = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width; float videoHeight = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height;
GIFSize optimalSize = GIFSizeMedium; if (videoWidth >= 1200 || videoHeight >= 1200)
optimalSize = GIFSizeVeryLow; else if (videoWidth >= 800 || videoHeight >= 800)
optimalSize = GIFSizeLow; else if (videoWidth >= 400 || videoHeight >= 400)
optimalSize = GIFSizeMedium; else if (videoWidth < 400|| videoHeight < 400)
optimalSize = GIFSizeHigh;
int frameCount = fltGifTime * kFrameInSecond;
//两帧的时间间隔
float increment = (float)fltGifTime/frameCount;
// Add frames to the buffer
NSMutableArray *timePoints = [NSMutableArray array]; for (int currentFrame = 0; currentFrame<frameCount; ++currentFrame) { float seconds = fltStartSecond + (float)increment * currentFrame; CMTime time = CMTimeMakeWithSeconds(seconds, 1 *NSEC_PER_SEC);
[timePoints addObject:[NSValue valueWithCMTime:time]];
}
[self createGIFforTimePoints:timePoints fromURL:videoURL fileProperties:fileProperties frameProperties:frameProperties gifImagePath:imagePath frameCount:frameCount gifSize:optimalSize];
}
- (NSURL *)createGIFforTimePoints:(NSArray *)timePoints fromURL:(NSURL *)url fileProperties:(NSDictionary *)fileProperties frameProperties:(NSDictionary *)frameProperties gifImagePath:(NSString *)imagePath frameCount:(int)frameCount gifSize:(GIFSize)gifSize{
NSURL *fileURL = [NSURL fileURLWithPath:imagePath]; if (fileURL == nil) return nil;
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)fileURL, kUTTypeGIF , frameCount, NULL); CGImageDestinationSetProperties(destination, (CFDictionaryRef)fileProperties);
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:nil]; AVAssetImageGenerator *generator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
generator.appliesPreferredTrackTransform = YES;
generator.requestedTimeToleranceBefore = kCMTimeZero;
generator.requestedTimeToleranceAfter = kCMTimeZero;
NSError *error = nil; CGImageRef previousImageRefCopy = nil; CGImageRef imageRef; NSLog(@"starat");
for (NSValue *time in timePoints) {
imageRef = [generator copyCGImageAtTime:[time CMTimeValue] actualTime:nil error:&error]; if((float)gifSize/10 != 1){
imageRef = createImageWithScale(imageRef, (float)gifSize/10);
}
if (error) {
_error =error; NSLog(@"Error copying image: %@", error); return nil;
} if (imageRef) { CGImageRelease(previousImageRefCopy);
previousImageRefCopy = CGImageCreateCopy(imageRef);
} else if (previousImageRefCopy) {
imageRef = CGImageCreateCopy(previousImageRefCopy);
} else {
_error =[NSError errorWithDomain:NSStringFromClass([self class]) code:0 userInfo:@{NSLocalizedDescriptionKey:@"Error copying image and no previous frames to duplicate"}]; NSLog(@"Error copying image and no previous frames to duplicate"); return nil;
} CGImageDestinationAddImage(destination, imageRef, (CFDictionaryRef)frameProperties); CGImageRelease(imageRef);
} NSLog(@"end"); CGImageRelease(previousImageRefCopy);
// Finalize the GIF
if (!CGImageDestinationFinalize(destination)) {
_error =error;
NSLog(@"Failed to finalize GIF destination: %@", error); if (destination != nil) { CFRelease(destination);
} return nil;
} CFRelease(destination);
return fileURL;
}#pragma mark - HelpersCGImageRef createImageWithScale(CGImageRef imageRef, float scale) {
#if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR
CGSize newSize = CGSizeMake(CGImageGetWidth(imageRef)*scale, CGImageGetHeight(imageRef)*scale); CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0); CGContextRef context = UIGraphicsGetCurrentContext(); if (!context) { return nil;
}
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(context, kCGInterpolationHigh); CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height);
CGContextConcatCTM(context, flipVertical); // Draw into the context; this scales the image
CGContextDrawImage(context, newRect, imageRef);
//Release old image
CFRelease(imageRef); // Get the resized image from the context and a UIImage
imageRef = CGBitmapContextCreateImage(context);
UIGraphicsEndImageContext();#endif
return imageRef;
}#pragma mark - Properties- (NSDictionary *)filePropertiesWithLoopCount:(int)loopCount { //GIF播放
//0不循环 1无限循环
return @{(NSString *)kCGImagePropertyGIFDictionary:
@{(NSString *)kCGImagePropertyGIFLoopCount: @(loopCount)}
};
}
- (NSDictionary *)framePropertiesWithDelayTime:(float)delayTime {
return @{(NSString *)kCGImagePropertyGIFDictionary:
@{(NSString *)kCGImagePropertyGIFDelayTime: @(delayTime)},
(NSString *)kCGImagePropertyColorModel:(NSString *)kCGImagePropertyColorModelRGB
};
}@end
作者：侯志桐
链接：https://www.jianshu.com/p/40728583ee00
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