当尝试将 opengl 视图快照作为 UIImage 进行多重采样时，图像颜色不同。
当多重采样关闭时，它是正确的。这就是我拍摄快照的方式：
- (UIImage*)snapshot
{
GLint backingWidth, backingHeight;
backingWidth = framebufferWidth;
backingHeight = framebufferHeight;
NSInteger myDataLength = backingWidth * backingHeight * 4;
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, backingWidth, backingHeight, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
// gl renders "upside down" so swap top to bottom into new array.
GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
for(int y = 0; y < backingHeight; y++) {
for(int x = 0; x < backingWidth * 4; x++) {
buffer2[y*4*backingWidth + x] = buffer[(backingHeight - y -1 ) * backingWidth * 4 + x];
}
}
// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, myProviderReleaseData);
// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * backingWidth;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast ;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// make the cgimage
CGImageRef imageRef = CGImageCreate(backingWidth, backingHeight, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
// then make the uiimage from that
UIImage *image1 = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
CGColorSpaceRelease(colorSpaceRef);
CGDataProviderRelease(provider);
free(buffer);
return image1;
}
这是拍摄快照的结果：
第一个是我正在绘制的 opengl 视图，第二个图像是我为上述代码获取的图像的快照。
我没有使用 GLKit 框架。想知道为什么多重采样会破坏快照。