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我不确定我的标题是否完全正确，但我不确定我的问题到底出在哪里。

我需要从 spritesheet 加载 UIImage 数组，然后将其用作 UIImageView 中的动画。

spritesheet 是使用 TexturePacker 生成的，TexturePacker 会生成巨大的图集 (2048x2048) 和带有 sprite 描述的 json。

到现在为止，我让它正常工作，甚至在 0.5-0.8 秒内加载 100 帧，这让我非常满意。

现在的问题是我需要从 Documents 文件夹中加载 spritesheets（它们已下载，因此无法集成到应用程序中），因此我必须UIImage imageWithContentsOfFile使用UIImage imagenamed. 这使我的加载时间增加了 5-15 秒，具体取决于动画中的帧数。我猜问题是因为图像没有被缓存，正在为每一帧加载它，但我不明白为什么

这是代码：

// With this line, perfect
//UIImage *atlas = [UIImage imageNamed:@"media/spritesheets/default-pro7@2x.png"];
// But with this one, incredibly looooong loading times
UIImage *atlas = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"media/spritesheets/default-pro7@2x" ofType:@"png"]];

CGImageRef atlasCGI = [atlas CGImage];

for( NSDictionary* dict in frames) {

    NSDictionary *frame = [dict objectForKey:@"frame"];
    int x = [[frame objectForKey:@"x"] intValue];
    int y = [[frame objectForKey:@"y"] intValue];
    int width = [[frame objectForKey:@"w"] intValue];
    int height = [[frame objectForKey:@"h"] intValue];

    NSDictionary *spriteSize = [dict objectForKey:@"spriteSourceSize"];
    int realx = [[spriteSize objectForKey:@"x"] intValue];

    NSDictionary *size = [dict objectForKey:@"sourceSize"];
    int realWidth = [[size objectForKey:@"w"] intValue];
    int realHeight = [[size objectForKey:@"h"] intValue];

    //Initialize the canvas size!
    canvasSize = CGSizeMake(realWidth, realHeight);

    bitmapBytesPerRow   = (canvasSize.width * 4);
    bitmapByteCount     = (bitmapBytesPerRow * canvasSize.height);

    bitmapData = malloc( bitmapByteCount );

    //Create the context
    context = CGBitmapContextCreate(bitmapData, canvasSize.width, canvasSize.height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);

    // Clear background
    CGContextClearRect(context,CGRectMake(0.0f,0.0f,canvasSize.width,canvasSize.height));

    // Get spriteRect
    CGRect cropRect = CGRectMake(x, y, width, height);
    CGImageRef imageRef = CGImageCreateWithImageInRect(atlasCGI, cropRect);

    //Draw the image into the bitmap context
    CGContextDrawImage(context, CGRectMake(realx, 0, width, height), imageRef);

    //Get the result image
    resultImage = CGBitmapContextCreateImage(context);

    UIImage *result = result = [UIImage imageWithCGImage:resultImage];

    [images addObject:result];

    //Cleanup
    free(bitmapData);
    CGImageRelease(resultImage);
    CGImageRelease(imageRef);
}

我什至可以尝试一个上传系统分析器会话，它显示在哪里加载了这么多时间

在此处输入图像描述

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1 回答 1

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Well, I finally figured out where the problem was. After looking more carefully with Instruments Time profiler, I noticed a lot of time was spent in copyImageBlockSetPNG , which was what made me believe first that I was loading the image from disk for every frame. turn out, somebody already had this problem Does CGContextDrawImage decompress PNG on the fly?, and it ended being true that I was loading the memory each frame, but not from disk, instead it was being uncompressed from memory in png format for every frame.

In that post theres a solution, which consists in writing the image to a context and getting from it an uncompressed copy of the image.

That works, but I found other way which I believe It's a little bit more efficient

NSDictionary *dict = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES]
                                             forKey:(id)kCGImageSourceShouldCache];
NSData *imageData = [NSData dataWithContentsOfFile:@"path/to/image.png"]];
CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)(imageData), NULL);
CGImageRef atlasCGI = CGImageSourceCreateImageAtIndex(source, 0, (__bridge CFDictionaryRef)dict);
CFRelease(source);

Hope it helps!

于 2013-03-10T19:22:32.390 回答