为图像添加边框 1 bpp 索引

Question

I want to add a border to an Image.

To achieve that, I want to crate a new empty image with size equal to old size + border size, copy old image on center and draw border :

There is the method I wrote :

private Bitmap addBorderToImage(Image image, int borderSize)
{
    Bitmap bmpTmp = new Bitmap(image);

    Bitmap bmp = new Bitmap(bmpTmp.Width + 2 * borderSize,
                            bmpTmp.Height + 2 * borderSize,
                            bmpTmp.PixelFormat);

    BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.WriteOnly, PixelFormat.Format1bppIndexed);
    BitmapData dataTmp = bmpTmp.LockBits(new Rectangle(0, 0, bmpTmp.Width, bmpTmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format1bppIndexed);
    // Copy the bytes from the image into a byte array
    for (int y = 0; y < bmpTmp.Height; y++)
    {
        System.Runtime.InteropServices.Marshal.Copy(dataTmp.Scan0, y * data.Stride, (IntPtr)((long)data.Scan0 + data.Stride * y + borderSize), y * data.Stride);
    }
    bmp.UnlockBits(data);
    bmpTmp.UnlockBits(data);

    using (Graphics g = Graphics.FromImage(bmp))
    {
        g.DrawRectangle(new Pen(Brushes.Green, borderSize * 2), new Rectangle(0, 0, bmp.Width, bmp.Height));
    }
    return bmp;
}

But I'm unable to do a correct copy. I have error :

Argument 1: cannot convert from 'System.IntPtr' to 'byte[]'

How should I do the Marshal.Copy ?

Edit: I use Marshall.copy instead of graphics cause I can't create graphics element from Format1bppIndexed.

Answer 1

First Marshal.Copy is expecting a byte [] array that's why it doesn't compile.

Second, you don't need to have low byte manipulation as Graphics handles all operation you need for this job (this is an authentic XY problem ).

Last, there are many undisposed object in your original code which will leads you to memory leaks.

What about the following :

    private static Bitmap AddBorderToImage(Image image, int borderSize)
    {
        using (Bitmap bmp = new Bitmap(image.Width + 2 * borderSize,
            image.Height + 2 * borderSize))
        {
            using (Graphics destGraph = Graphics.FromImage(bmp))
            {
                destGraph.FillRectangle(Brushes.Green, new Rectangle(new Point(0, 0), bmp.Size));
                destGraph.DrawImage(image, new Point(borderSize, borderSize));
            }

            return bmp.Clone(new Rectangle(0, 0, bmp.Width, bmp.Height), image.PixelFormat);
        }
    }

The idea is as simple as this:

• Create a new result bitmap with the background of border's color
• Draw the inner original image at the correct place ( borderSize , borderSize ).
• Clone the final result with original PixelFormat

Answer 2

I used System.Drawing and got the results. Hope this is what you were looking for.

private Bitmap AddBorder(Image original_image, int border_size, Color border_color)
    {
        Size originalSize = new Size(original_image.Width + border_size, original_image.Height + border_size);
        Bitmap bmp = new Bitmap(originalSize.Width, originalSize.Height);
        Rectangle rec = new Rectangle(new Point(0, 0), originalSize);
        Pen pen = new Pen(border_color, border_size);
        Graphics g = Graphics.FromImage(bmp);
        g.DrawRectangle(pen, rec);
        rec.Inflate(-border_size /2, -border_size /2);
        g.DrawImage(original_image, rec);
        return bmp;
    }