Question

我通过使其外部区域变暗来绘制矩形ROI区域，如图http://www.codeproject.com/script/Membership/Uploads/4613314/roi.jpg

但是image.MakeTransparent需要花费太多时间。提高绘图速度的最佳方法是什么？

void DrawRoi(Bitmap Image, RectangleF rect)
{
        Rectangle roi = new Rectangle();

        roi.X = (int)((float)Image.Width * rect.X);
        roi.Y = (int)((float)Image.Height * rect.Y);
        roi.Width = (int)((float)Image.Width * rect.Width);
        roi.Height = (int)((float)Image.Height * rect.Height);

        Stopwatch timer = new Stopwatch();
        timer.Start();
        // graphics manipulation takes about 240ms on 1080p image
        using (Bitmap roiMaskImage = CreateRoiMaskImage(ImageWithRoi.Width, ImageWithRoi.Height, roi))
        {
                using (Graphics g = Graphics.FromImage(ImageWithRoi))
                {                                
                        g.DrawImage(Image, 0, 0);
                        g.DrawImage(roiMaskImage, 0, 0);
                        Pen borderPen = CreateRoiBorderPen(ImageWithRoi);
                        g.DrawRectangle(borderPen, roi);
                }
        }
        Debug.WriteLine("roi graphics: {0}ms", timer.ElapsedMilliseconds);
        this.imagePictureBox.Image = ImageWithRoi;
}

Bitmap CreateRoiMaskImage(int width, int height, Rectangle roi)
{
        Bitmap image = new Bitmap(width, height, PixelFormat.Format32bppArgb);
        using (Graphics g = Graphics.FromImage(image))
        {
                SolidBrush dimBrush = new SolidBrush(Color.FromArgb(64, 0, 0, 0));
                g.FillRectangle(dimBrush, 0, 0, width, height);
                SolidBrush roiBrush = new SolidBrush(Color.Red);
                g.FillRectangle(roiBrush, roi);
                image.MakeTransparent(Color.Red);
                return image;
        }                
}

Pen CreateRoiBorderPen(Bitmap image)
{
        float width = ((float)(image.Width + image.Height) * 2.5f) / (float)(640 + 480);
        if (width < 1.0f)
                width = 1.0f;
        Pen pen = new Pen(Color.FromArgb(255, 0, 255, 0), width);
        return pen;
}

Answer 1

根本不操纵图像。只需在图像上绘制“调光”即可。您可以通过

实现相同的效果

1）在整个图像上绘制一个大的半透明区域，剪辑区域设置为您的投资回报率

// Assume for simplicity the image is size w*h, and the graphics is the same size. 
// The ROI is a rectangle named roiRect.
g.DrawImageUnscaled(image, 0, 0 , w, h);
g.SetClip(roiRect);
g.FillRectangle(new SolidBrush(Color.FromArgb(128, Color.Black)), 0, 0, w, h);
g.ResetClip();

2）绘制图像，然后绘制变暗矩形，然后绘制图像的roi部分。

3）在顶部/右侧/左侧/底部绘制4个单独的矩形，以省去您的投资回报率。

Answer 2

我无法看到调用.MakeTransparent的任何一点。创建蒙版图像时

Bitmap image = new Bitmap(width, height, PixelFormat.Format32bppArgb);

它已经透明了。最好将dimBrush绘制为四个单独的矩形（ROI上/下/左边的区域），避免在已经透明的区域中绘制！

Answer 3

看看WriteableBitmap类。在WritePixels方法中，您可以使用Int32Rect定义ROI。

优化图像中的感兴趣区域（ROI）

3 个答案: