<Error>: CGBitmapContextCreateImage: invalid context 0x0. 解决方案

最新推荐文章于 2021-12-30 18:48:37 发布

yanglei3kyou

最新推荐文章于 2021-12-30 18:48:37 发布

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分类专栏： iOS 文章标签： CG_CONTEXT_SHOW_BACK invalid context 0x0 Error

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在使用AVAssetReader+AVAssetReaderTrackOutput处理视频并尝试将CMSampleBufferRef转换为CGImageRef时，遇到了 '<Error>: CGBitmapContextCreateImage: invalid context 0x0.' 的错误。错误通常由于高度或宽度为0导致。解决方案是在创建内容画布时添加逻辑判断，避免高度或宽度为0的情况，从而消除错误。参考了Stack Overflow和4byte.cn的相关讨论。

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阐述

最近研究 AVAssetReader+AVAssetReaderTrackOutput 用其写自己的视频播放类。编写中CMSampleBufferRef转换 CGImageRef 的时候产生一些 Error，如下方:

<Error>: CGBitmapContextCreateImage: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

 <Error>: CGBitmapContextCreateImage: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

 相关代码

- (CGImageRef)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer {
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0);
    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    //Generate image to edit
    unsigned char* pixel = (unsigned char *)CVPixelBufferGetBaseAddress(imageBuffer);
    CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB();
    CGContextRef context=CGBitmapContextCreate(pixel, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little|kCGImageAlphaPremultipliedFirst);
    CGImageRef image = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    return image;
}