Transparency

This morning I googled around for "standard transparency colors" in hopes that I would find a color key that is typically used to represent transparency in images. In .NET CF, the only way to make part of an image transparent is through the following code:

ImageAttributes attr = new ImageAttributes();
attr.SetColorKey(Color.White, Color.White);
Rectangle rDest = new Rectangle(xImage, yImage, Image.Width, Image.Height);
g.DrawImage(Image, rDest, 0, 0, Image.Width, Image.Height, GraphicsUnit.Pixel, attr);

In this case, the color "white" would be made transparent in the given Image. Note that although SetColorKey allows the developer to specify a transparency color range, I believe that this range is limited to one color on .NET CF. During my search, I found that the standard chroma key is "bright pink." However, it's also convention to automatically select the chroma key based on the upper-left hand corner pixel of the image, in hopes that this is representative of the "background" pixels. Here's a post by Ed Kaim (MSFT) that really explains this well imo.

"However, the issue you're raising is why Microsoft recommends the usage of ImageAttributes in order to draw transparency, and why the top left pixel is called out as a prime source. First of all, ImageAttributes is the only feasible way to draw transparency in managed code on the .NET Compact Framework. Otherwise you'd have to go pixel by pixel and only draw the nontransparent ones, which would be slow and painful. The reason the top left pixel is offered is because it's often transparent in images with transparency. Sure, it's not *always* transparent, but it's usually transparent, due to its location in the image and the fact that most pictures on buttons don't go all the way to the top left border. However, you can decide that your standard chroma key color is bright pink (as many do) and hardcode your ImageAttributes object to use that color for all images, provided you do the work in the art to make sure the same exact color is used on the transparent spots in your files, whatever format they may be."