仅显示最后一帧以进行显示

Question

我正在尝试使用前景侦测器r对我的视频应用背景减法。但是 imshow 仅在最后一帧显示它。任何帮助将不胜感激

foregroundDetector = vision.ForegroundDetector('NumGaussians', 3, ...'NumTrainingFrames', 100);
videoReader = vision.VideoFileReader('test1.mp4');
for i = 1:120
    frame = step(videoReader); % read the next video frame
%     imshow(frame);
    disp(i);
 foreground = step(foregroundDetector, frame);
    imshow(foreground);
end

Answer 1

为了防止不必要的图形处理，如果在循环中不断更新图形对象，则在显式执行暂停之前，不会实际呈现图形 drawnow 用于强制刷新事件队列。

for k = 1:120
    frame = step(videoReader); % read the next video frame
    foreground = step(foregroundDetector, frame);
    imshow(foreground);
    % Explicitly force the renderer to update the display
    drawnow
end

作为旁注，为了获得更好的性能，您应该更新现有的图像对象，而不是使用 imshow 不断创建新的图像对象。

frame = step(videoReader);
foreground = step(foregroundDetector, frame);
him = imshow(foreground);
for k = 1:119
    set(him, 'CData', foreground)
    drawnow
    frame = step(videoReader); % read the next video frame
    foreground = step(foregroundDetector, frame);
end