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我使用的像素颜色挑选摸出我点击了其中的OpenGL对象，只要我打开GLKViewDrawableMultisample4X在视图它出色的作品IOS GLKit：图灵GLKViewDrawableMultisample4X停止对象采摘
，采摘停止工作？
我试着打开和关闭，当我触摸屏幕，但只能工作一次。
采摘代码：
GLKView *glkView = (GLKView*)[self view];
UIImage *snapshot = [glkView snapshot];
GLKVector4 colour = [snapshot pickPixelAtX:xPos Y:yPos];
@implementation UIImage (NDBExtensions)
- (GLKVector4)pickPixelAtX:(NSUInteger)x Y:(NSUInteger)y {
CGImageRef cgImage = [self CGImage];
size_t width = CGImageGetWidth(cgImage);
size_t height = CGImageGetHeight(cgImage);
if ((x < width) && (y < height))
{
CGDataProviderRef provider = CGImageGetDataProvider(cgImage);
CFDataRef bitmapData = CGDataProviderCopyData(provider);
const UInt8* data = CFDataGetBytePtr(bitmapData);
size_t offset = ((width * y) + x) * 4;
UInt8 b = data[offset+0];
UInt8 g = data[offset+1];
UInt8 r = data[offset+2];
UInt8 a = data[offset+3];
CFRelease(bitmapData);
return GLKVector4Make(r, g, b, a);
}
return GLKVector4Make(0,0,0,0);
}