c# - 使用 pictureBox sizeMode 裁剪位图克隆已缩放

Question

我在网上找到这个裁剪图片的功能，如果pictureBox source sizeMode正常就可以了。但是当 pictureBox sizeMode 缩放时，它仍然像正常 sizeMode 一样被克隆。

如何克隆与缩放后的图片框相同？不是原始普通位图的大小？

public static Bitmap CropBitmap(Bitmap bitmap, int x, int y, int w, int h)
{
    Rectangle rect = new Rectangle(x, y, w, h);
    Bitmap cropped = bitmap.Clone(rect, bitmap.PixelFormat);
    return cropped;
}

像这样使用

pictureBox2.Image = CropBitmap((Bitmap)pictureBox1.Image.Clone(), 35, 0, 110, 150);

Answer 1

最简单的方法是使用 DrawToBitmap方法从图片框获取输出，而不考虑 SizeMode，然后像这样裁剪输出:

public static Bitmap Crop(PictureBox pb, int x, int y, int w, int h)
{
    var rect = pb.ClientRectangle;
    using (var output = new Bitmap(rect.Width, rect.Height, pb.Image.PixelFormat))
    {
        pb.DrawToBitmap(output, rect);
        return output.Clone(new Rectangle(x, y, w, h), output.PixelFormat);
    }
}

但是，上述方法的缺点是它确实会裁剪可能缩放的图像。

如果您确实想要裁剪原始图像，您需要将传递的矩形(我假设它在图片框客户端坐标中)映射到原始图像坐标。

如果图片框提供一个方法ClientToImage就好了(类似于ClientToScreen)，但是没有，所以我们需要提取 Reference Source 中的 SizeMode 逻辑.

新方法是这样的:

public static class ImageUtils
{
    public static Bitmap CropImage(this PictureBox pb, int x, int y, int w, int h)
    {
        var imageRect = pb.GetImageRectangle();
        var image = pb.Image;
        float scaleX = (float)image.Width / imageRect.Width;
        float scaleY = (float)image.Height / imageRect.Height;
        var cropRect = new Rectangle();
        cropRect.X = Scale(x - imageRect.X, scaleX, image.Width);
        cropRect.Y = Scale(y - imageRect.Y, scaleY, image.Height);
        cropRect.Width = Scale(w, scaleX, image.Width - cropRect.X);
        cropRect.Height = Scale(h, scaleY, image.Height - cropRect.Y);
        var result = new Bitmap(cropRect.Width, cropRect.Height, image.PixelFormat);
        using (var g = Graphics.FromImage(result))
            g.DrawImage(image, new Rectangle(new Point(0, 0), cropRect.Size), cropRect, GraphicsUnit.Pixel);
        return result;
    }

    static int Scale(int value, float scale, int maxValue)
    {
        int result = (int)(value * scale);
        return result < 0 ? 0 : result > maxValue ? maxValue : result;
    }

    public static Rectangle GetImageRectangle(this PictureBox pb)
    {
        var rect = pb.ClientRectangle;
        var padding = pb.Padding;
        rect.X += padding.Left;
        rect.Y += padding.Top;
        rect.Width -= padding.Horizontal;
        rect.Height -= padding.Vertical;
        var image = pb.Image;
        var sizeMode = pb.SizeMode;
        if (sizeMode == PictureBoxSizeMode.Normal || sizeMode == PictureBoxSizeMode.AutoSize)
            rect.Size = image.Size;
        else if (sizeMode == PictureBoxSizeMode.CenterImage)
        {
            rect.X += (rect.Width - image.Width) / 2;
            rect.Y += (rect.Height - image.Height) / 2;
            rect.Size = image.Size;
        }
        else if (sizeMode == PictureBoxSizeMode.Zoom)
        {
            var imageSize = image.Size;
            var zoomSize = pb.ClientSize;
            float ratio = Math.Min((float)zoomSize.Width / imageSize.Width, (float)zoomSize.Height / imageSize.Height);
            rect.Width = (int)(imageSize.Width * ratio);
            rect.Height = (int)(imageSize.Height * ratio);
            rect.X = (pb.ClientRectangle.Width - rect.Width) / 2;
            rect.Y = (pb.ClientRectangle.Height - rect.Height) / 2;
        }
        return rect;
    }
}