Question

我正在使用xcode，目前正在尝试使用以下代码从像素缓冲区中提取像素值。但是，当我打印出像素值时，它由负值组成。以前有人遇到过这样的问题吗？

部分代码如下

- (void)captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:
(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{

CVImageBufferRef Buffer = CMSampleBufferGetImageBuffer(sampleBuffer);

CVPixelBufferLockBaseAddress(Buffer, 0);
uint8_t* BaseAddress = (uint8_t*)CVPixelBufferGetBaseAddressOfPlane(Buffer, 0);
size_t Width = CVPixelBufferGetWidth(Buffer);
size_t Height = CVPixelBufferGetHeight(Buffer);
if (BaseAddress)
{
    IplImage* Temporary = cvCreateImage(cvSize(Width, Height), IPL_DEPTH_8U, 4);

    Temporary->imageData = (char*)BaseAddress;
    for (int i = 0; i < Temporary->width * Temporary->height; ++i) {
        NSLog(@"Pixel value: %d",Temporary->imageData[i]);
        //where i try to print the pixels
    }
}

Answer 1

问题是imageData IplImage是签名char。因此，任何大于127的内容都将显示为负数。

您可以简单地将其分配给unsigned char，然后打印出来，并且您会看到0到255之间的值，就像您可能预料到的那样：

for (int i = 0; i < Temporary->width * Temporary->height; ++i) {
    unsigned char c = Temporary->imageData[i];
    NSLog(@"Pixel value: %u", c);
}

或者你可以用十六进制打印：

NSLog(@"Pixel value: %02x", c);

xcode CVpixelBuffer显示负值

1 个答案: