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Re: Any function to draw gradient color? [message #12043 is a reply to message #12039]

Tue, 09 October 2007 15:23

mrjt
Messages: 705
Registered: March 2007
Location: London

Contributor

I obviously don't know as much about this as Mirek, but in the interests of a quick answer I'll tell you what I know and he can correct me later Smile

As I understand the only way of drawing to the alpha channel is using DrawImage. You can create an image in the usual ways or, if you want to draw primitives with an alpha channel Mirek suggests something like:

	virtual void Paint(Draw& draw)
	{
		draw.DrawRect(GetSize(), SColorFace());

		ImageDraw img(200, 100);	
		img.Alpha().DrawRect(0, 0, 200, 100, Color(128, 0, 0));
		img.Alpha().DrawText(0, 0, "This is the alpha channel", StdFont(), Color(0, 0, 0));
		img.DrawRect(0, 0, 200, 100, Red());

		draw.DrawImage(1, 1, img);
	}

Note that:
- The alpha channel is initially all 0 (hence the first DrawRect above)
- When drawing to Alpha(), only the red channel is used for the alpha value.

If you only want alpha gradients you may want to look at CreateHorzFadeOut/HorzFadeOut (I believe the second caches the created image).

James

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