Question

我试图在AVCapture预览图层中显示每个帧，我想基本上使用openCV来检测特定形状（更具体地说是圆圈）并在屏幕上将它们绘制给用户。我似乎无法获得更新屏幕预览图层的正确方法，相反，我只能从队列中获取输出帧，这对预览没有任何作用。

目前使用以下方法从输出缓冲区中提取帧：

    // Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0);

    // Get the number of bytes per row for the pixel buffer
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);

    // Create a device-dependent RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                 bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return image;
    }

有没有办法让每个发送的帧都显示在预览图层上？或使用AVCapture会话而不是opencv相机实现霍夫检测的任何其他方法？任何帮助都会非常感激！

Answer 1

要做到这一点，最好的方法是从方法中取出每一帧：

- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer;

在此方法中提取UIImage并使用包含OpenCV的包装器在每个帧中查找houghcircles。霍夫圆圈将生成圆圈所在位置的坐标（如果有）。然后，我可以使用圆圈的位置在视图上绘制CAShapeLayer以显示圆圈。我使用以下内容在视图中绘制圆圈：

circleLayer = [CAShapeLayer layer];
[circleLayer setPath:[[UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, radius, radius)] CGPath]];
[self.previewLayer addSublayer:circleLayer];
[circleLayer setStrokeColor:[[UIColor redColor] CGColor]];
[circleLayer setFillColor:[[UIColor clearColor] CGColor]];

我们可以根据openCV算法检测到houghcircle的位置简单地移动圆圈，如下所示：

[circleLayer setPosition:CGPointMake(x,y)];

可能需要根据捕获的图像的方向和缩放因子来调整CGPoint的参数。这个解决方案有效！

通过提取帧在avcapture预览图层上绘制形状

1 个答案: