dwm - Aero: How to draw solid (opaque) colors on glass?

Question

Using GDI+ to draw various colors:

brush = new SolidBrush(color);
graphics.FillRectangle(brush, x, y, width, height);

You'll notice that no opaque color shows properly on glass:

How do i draw solid colors on glass?

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You'll also notice that a fully opaque color is handled differently depending on what color it is:

• opaque black: fully transparent
• opaque color: partially transparent
• opaque white: fully opaque

Can anyone point me to the documentation on the desktop compositor that explains how different colors are handled?

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Update 3

You'll also notice that FillRectangle behaves differently than FillEllipse:

• FillEllipse with an opaque color draws an opaque color
• FillRectangle with an opaque color draws partially (or fully) transparent

Explanation for non-sensical behavior please.

Update 4

Alwayslearning suggested i change the compositing mode. From MSDN:

CompositingMode Enumeration

The CompositingMode enumeration specifies how rendered colors are combined with background colors. This enumeration is used by the Graphics::GetCompositingMode and 'Graphics::SetCompositingMode' methods of the Graphics class.

CompositingModeSourceOver

Specifies that when a color is rendered, it is blended with the background color. The blend is determined by the alpha component of the color being rendered.

CompositingModeSourceCopy

Specifies that when a color is rendered, it overwrites the background color. This mode cannot be used along with TextRenderingHintClearTypeGridFit.

From the description of CompositingModeSourceCopy, it sounds like it's not the option i want. From the limitations it imposes, it sounds like the option i want. And with composition, or transparency disabled it isn't the option i want, since it performs a SourceCopy, rather than SourceBlend:

Fortunately it's not an evil i have to contemplate because it doesn't solve my actual issue. After constructing my graphics object, i tried changed the compositing mode:

graphics = new Graphics(hDC);
graphics.SetCompositingMode(CompositingModeSourceCopy); //CompositingModeSourceCopy = 1

The result has no effect on the output:

Notes

• Win32 native
• not .NET (i.e. native)
• not Winforms (i.e. native)
• GDI+ (i.e. native)

See also

• Aero: How to draw ClearType text on glass?
• Windows Aero: What color to paint to make “glass” appear?
• Vista/7: How to get glass color?

Answer 1

Seems to work OK for me. With the lack of a full code example I'm assuming you've got your compositing mode wrong.

public void RenderGdiPlus()
{
    List<string> colors = new List<string>(new string[] { "000000", "ff0000", "00ff00", "0000ff", "ffffff" });
    List<string> alphas = new List<string>(new string[] { "00", "01", "40", "80", "c0", "fe", "ff" });
    Bitmap bmp = new Bitmap(200, 300, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

    Graphics graphics = Graphics.FromImage(bmp);
    graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
    graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.None;
    graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;

    graphics.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
    graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
    SolidBrush backBrush = new SolidBrush(Color.FromArgb(254, 131, 208, 129));
    graphics.FillRectangle(backBrush, 0, 0, 300, 300);

    graphics.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver;
    Pen pen = new Pen(Color.Gray);
    for (int row = 0; row < alphas.Count; row++)
    {
        string alpha = alphas[row];
        for (int column=0; column<colors.Count; column++)
        {
            string color = "#" + alpha + colors[column];
            SolidBrush brush = new SolidBrush(ColorTranslator.FromHtml(color));
            graphics.DrawRectangle(pen, 40*column, 40*row, 32, 32);
            graphics.FillRectangle(brush, 1+40*column, 1+40*row, 31, 31);
        }
    }

    Graphics gr2 = Graphics.FromHwnd(this.Handle);
    gr2.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
    gr2.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
    gr2.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.None;
    gr2.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;
    gr2.DrawImage(bmp, 0, 0);
}