我正在创建一个每秒拍摄一张照片并将图像保存到磁盘的应用程序。当拍摄了足够多的照片时,该应用程序会使用 AVFoundation 框架创建图像视频。这是通过为每个图像创建一个图层来完成的,添加一个动画,在一段时间后隐藏该图层,然后将这些图层组合成一个由AVVideoCompositionCoreAnimationTool
. 创建一个AVVideoComposition
包含动画工具的文件后,我最终将使用AVAssetExportSession
导出一个AVMutableComposition
.
但是,在创建图层时,如果我有 50-60 张或更多照片,我的应用程序会发出两个内存警告,然后崩溃。我使用下面的代码来创建图层。这意味着对于 60 张图像,下面的循环将运行 60 次。每个图像一次。使用照片的imageLayer
内容创建,将动画应用于图层,然后将图层作为子图层添加到layer
.
CALayer *layer = [CALayer layer];
layer.frame = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
layer.bounds = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
for (NSString *imagePath in imagePaths)
{
CMTime endTime = CMTimeAdd(cursorTime, CMTimeMake(1.0f, (CGFloat)fps));
UIImage *theImage = [[UIImage alloc] initWithContentsOfFile:imagePath];
CGFloat scaleFactor = MIN(renderSize.width / theImage.size.width, renderSize.height / theImage.size.height);
CGSize newSize = CGSizeMake(theImage.size.width * scaleFactor, theImage.size.height * scaleFactor);
UIImage *resizedImage = [theImage resizedImageToSize:newSize];
CGImageRef image = resizedImage.CGImage;
CGSize imageSize = resizedImage.size;
CALayer *imageLayer = [CALayer layer];
imageLayer.frame = CGRectMake((renderSize.width - imageSize.width) * 0.50f, (renderSize.height - imageSize.height) * 0.50f, imageSize.width, imageSize.height);
imageLayer.bounds = CGRectMake((renderSize.width - imageSize.width) * 0.50f, (renderSize.height - imageSize.height) * 0.50f, imageSize.width, imageSize.height);
imageLayer.contents = (__bridge id)image;
imageLayer.beginTime = (CGFloat)cursorTime.value / (CGFloat)cursorTime.timescale;
CABasicAnimation *hideAnimation = [CABasicAnimation animationWithKeyPath:@"hidden"];
hideAnimation.fromValue = @(NO);
hideAnimation.toValue = @(YES);
hideAnimation.additive = NO;
hideAnimation.removedOnCompletion = NO;
hideAnimation.beginTime = (CGFloat)endTime.value / (CGFloat)endTime.timescale;
hideAnimation.fillMode = kCAFillModeBoth;
[imageLayer addAnimation:hideAnimation forKey:nil];
[layer addSublayer:imageLayer];
cursorTime = endTime;
}
似乎是这段代码使用了太多内存。谁能告诉我如何优化代码或以任何其他方式避免内存警告并最终避免崩溃?
每个Daij -Djans 答案的更新。
自动释放池并没有改变任何事情。我尝试编写自定义图层并自己绘制图像。这确实允许我渲染更多图像,但它最终仍然会发出内存警告并使应用程序崩溃。事实证明,-drawInContext:
除非-setNeedsDisplay
在图层上调用,否则不会调用。该类如下所示:
PhotoLayer.h
#import <QuartzCore/QuartzCore.h>
@interface PhotoLayer : CALayer
@property (nonatomic, copy) NSString *path;
@end
PhotoLayer.m
#import "PhotoLayer.h"
#import <ImageIO/ImageIO.h>
@implementation PhotoLayer
- (void)drawInContext:(CGContextRef)context
{
[super drawInContext:context];
// Retrieve image from file path
CGDataProviderRef dataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef)[NSData dataWithContentsOfFile:self.path]);
CGImageRef image = CGImageCreateWithJPEGDataProvider(dataProvider, NULL, TRUE, kCGRenderingIntentDefault);
CGSize imageSize = CGSizeMake(CGImageGetWidth(image), CGImageGetHeight(image));
// Create transformation for orientation
CGImageSourceRef source = CGImageSourceCreateWithDataProvider(dataProvider, NULL);
CFDictionaryRef dictionaryRef = CGImageSourceCopyPropertiesAtIndex(source, 0, NULL);
CGAffineTransform transform;
NSInteger orientation = [(NSNumber *)CFDictionaryGetValue(dictionaryRef, kCGImagePropertyOrientation) integerValue];
switch (orientation) {
case 1:
// Flip vertically
transform = CGAffineTransformMake(1.0f, 0.0f, 0.0f, -1.0f, 0.0f, self.bounds.size.height);
break;
case 3:
// Flip horizontally
transform = CGAffineTransformMake(-1.0f, 0.0f, 0.0f, 1.0f, self.bounds.size.width, 0.0f);
break;
case 6:
// Rotate 90 degrees and flip vertically
transform = CGAffineTransformMake(0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f);
break;
case 8:
// Rotate -90 degrees and flip vertically
transform = CGAffineTransformMake(0.0f, -1.0f, -1.0f, 0.0f, self.bounds.size.height, self.bounds.size.width);
break;
default:
// Unknown orientation, consider landscape right
transform = CGAffineTransformMake(1.0f, 0.0f, 0.0f, -1.0f, 0.0f, self.bounds.size.height);
NSLog(@"Unknown orientation when drawing image in layer.");
break;
}
// Calculate amount to scale image
CGFloat scaleFactor = MIN(self.bounds.size.width / imageSize.width, self.bounds.size.height / imageSize.height);
// Calculate new size and positiondepending on orientation
CGSize newSize = CGSizeZero;
CGPoint pos = CGPointZero;
if (orientation == 1 || orientation == 3)
{
newSize = CGSizeMake(imageSize.width * scaleFactor, imageSize.height * scaleFactor);
pos = CGPointMake((self.bounds.size.width - newSize.width) * 0.50f, (self.bounds.size.height - newSize.height) * 0.50f);
}
else
{
imageSize = CGSizeMake(imageSize.height, imageSize.width);
newSize = CGSizeMake(imageSize.height * scaleFactor, imageSize.width * scaleFactor);
pos = CGPointMake((self.bounds.size.height - newSize.width) * 0.50f, (self.bounds.size.width - newSize.height) * 0.50f);
}
// Apply transformation
CGContextConcatCTM(context, transform);
// Draw image
CGContextDrawImage(context, CGRectMake(pos.x, pos.y, newSize.width, newSize.height), image);
// Clean up
CGDataProviderRelease(dataProvider);
CGImageRelease(image);
CFRelease(source);
CFRelease(dictionaryRef);
}
- (void)dealloc
{
_path = nil;
}
@end
然后我使用下面的图层。我没有设置图层的内容,而是设置了图像的路径并绘制它。要绘制它,我需要调用-setNeedsDisplay
.
CALayer *layer = [CALayer layer];
layer.frame = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
layer.bounds = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
for (NSString *imagePath in imagePaths)
{
@autoreleasepool {
CMTime endTime = CMTimeAdd(cursorTime, CMTimeMake(1.0f, (CGFloat)fps));
PhotoLayer *photoLayer = [[PhotoLayer alloc] init];
photoLayer.path = imagePath;
photoLayer.frame = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
photoLayer.bounds = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
photoLayer.beginTime = (CGFloat)cursorTime.value / (CGFloat)cursorTime.timescale;
CABasicAnimation *hideAnimation = [CABasicAnimation animationWithKeyPath:@"hidden"];
hideAnimation.fromValue = @(NO);
hideAnimation.toValue = @(YES);
hideAnimation.additive = NO;
hideAnimation.removedOnCompletion = NO;
hideAnimation.beginTime = (CGFloat)endTime.value / (CGFloat)endTime.timescale;
hideAnimation.fillMode = kCAFillModeBoth;
[photoLayer addAnimation:hideAnimation forKey:nil];
[layer addSublayer:photoLayer];
[photoLayer setNeedsDisplay];
cursorTime = endTime;
}
}
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
videoLayer.frame = CGRectMake(0.0f, 0.0f, renderSize.width, renderSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:layer];