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我正在尝试在 iPhone 上截取 GLView 的屏幕截图。我写了以下代码：

[self setContext];

GLint backWidth, backHeight;

glGetRenderbufferParameterivOES( GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backWidth );
glGetRenderbufferParameterivOES( GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backHeight );

int         dataLength  = backWidth * backHeight * 4;
uint32_t*   pData       = (uint32_t*)malloc( dataLength * sizeof( char ) );
memset( pData, 0xff, dataLength ); // This is here to confirm some writing occurs in glReadPixels

// Read pixel data from the framebuffer
//glPixelStorei( GL_PACK_ALIGNMENT, 4 );
glReadPixels( 0, 0, backWidth, backHeight, GL_RGBA, GL_UNSIGNED_BYTE, pData );
fprintf( stderr, "%d\n", glGetError() );

CGDataProviderRef   cgDataProvider  = CGDataProviderCreateWithData( NULL, pData, dataLength, DataProviderReleaseDataCallback );
CGColorSpaceRef     cgColorSpace    = CGColorSpaceCreateDeviceRGB();
CGImageRef          cgImage         = CGImageCreate(    backWidth, backHeight, 8, 32, backWidth * 4, cgColorSpace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
                                                        cgDataProvider, NULL, true, kCGRenderingIntentDefault );

//NSData*       pNSData         = [[NSData alloc] initWithBytes: pData length: dataLength];
UIImage*    pRetImage       = [UIImage imageWithCGImage: cgImage scale: 1.0f orientation: UIImageOrientationDownMirrored];
CFRelease( cgDataProvider );
CFRelease( cgColorSpace );
CGImageRelease( cgImage );
//free( pData );

return pRetImage;

在模拟器中完美运行。不幸的是，当我尝试在 iPhone 4S glReadPixels 上运行它时，什么也没做。我故意将数组设置为 0xff 以查看是否可以查看它是否在做任何事情，而我将数组设置为什么也没关系 glReadPixels 什么都不做。它也不会报告任何错误。

除非 iPhone 为我进行设置，否则我不会使用多重采样缓冲区。

glGenRenderbuffers( 1, &mGlRenderBuffer );
glBindRenderbuffer( GL_RENDERBUFFER, mGlRenderBuffer );

[mGlContext renderbufferStorage: GL_RENDERBUFFER fromDrawable: mGlLayer];

GLuint frameBuffer;
glGenFramebuffers( 1, &frameBuffer );
glBindFramebuffer( GL_FRAMEBUFFER, frameBuffer );
glFramebufferRenderbuffer( GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, mGlRenderBuffer );

有没有人知道发生了什么？它让我发疯:(

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1 回答 1

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原来是 iOS6 对设置 kEAGLDrawablePropertyRetainedBacking 有点挑剔...

eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSNumber numberWithBool:YES],
                                    kEAGLDrawablePropertyRetainedBacking,
                                    kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat,
                                    nil];

看这里

于 2012-11-06T16:06:04.880 回答