/// <summary>
/// Special draw logic to draw transparent text using GDI.<br/>
/// 1. Create in-memory DC<br/>
/// 2. Copy background to in-memory DC<br/>
/// 3. Draw the text to in-memory DC<br/>
/// 4. Copy the in-memory DC to the proper location with alpha blend<br/>
/// </summary>
private static void DrawTransparentText(IntPtr hdc, string str, RFont font, Point point, Size size, Color color)
{
IntPtr dib;
var memoryHdc = Win32Utils.CreateMemoryHdc(hdc, size.Width, size.Height, out dib);
try
{
// copy target background to memory HDC so when copied back it will have the proper background
Win32Utils.BitBlt(memoryHdc, 0, 0, size.Width, size.Height, hdc, point.X, point.Y, Win32Utils.BitBltCopy);
// Create and select font
Win32Utils.SelectObject(memoryHdc, ((FontAdapter)font).HFont);
Win32Utils.SetTextColor(memoryHdc, (color.B & 0xFF) << 16 | (color.G & 0xFF) << 8 | color.R);
// Draw text to memory HDC
Win32Utils.TextOut(memoryHdc, 0, 0, str, str.Length);
// copy from memory HDC to normal HDC with alpha blend so achieve the transparent text
Win32Utils.AlphaBlend(hdc, point.X, point.Y, size.Width, size.Height, memoryHdc, 0, 0, size.Width, size.Height, new BlendFunction(color.A));
}
finally
{
Win32Utils.ReleaseMemoryHdc(memoryHdc, dib);
}
}
/// <summary>
/// Copy all the bitmap bits from memory bitmap buffer to the given image.
/// </summary>
/// <param name="memoryHdc">the source memory bitmap buffer to copy from</param>
/// <param name="image">the destination bitmap image to copy to</param>
private static void CopyBufferToImage(IntPtr memoryHdc, Image image)
{
using (var imageGraphics = Graphics.FromImage(image)) {
var imgHdc = imageGraphics.GetHdc();
Win32Utils.BitBlt(imgHdc, 0, 0, image.Width, image.Height, memoryHdc, 0, 0, Win32Utils.BitBltCopy);
imageGraphics.ReleaseHdc(imgHdc);
}
}