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标题: ios - xcode CVpixelBuffer 显示负值 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-13 05:00
标题: ios - xcode CVpixelBuffer 显示负值

我正在使用 xcode，目前正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。有人遇到过这样的问题吗？

部分代码如下

- (void)captureOutputAVCaptureOutput*)captureOutput didOutputSampleBuffer:
(CMSampleBufferRef)sampleBuffer fromConnectionAVCaptureConnection*)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(@"ixel value: %d",Temporary->imageData[i]);
        //where i try to print the pixels
    }
}

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Best Answer-推荐答案

问题是 IplImage 的 imageData 是签名的 char。因此，任何大于 127 的都将显示为负数。

您可以简单地将其分配给 unsigned char，然后将其打印出来，您将看到 0 到 255 之间的值，正如您可能预期的那样:

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

或者你可以用十六进制打印:

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

关于ios - xcode CVpixelBuffer 显示负值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28150512/

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