Re: [GD-DEVEL] Using brushes with alpha transparency...

Hi Pierre: I created a little test program and some brushes. You can nab them at:

  ftp://ftp.dnr.state.mn.us/pub/brushtest.zip

The archive contains 3 variable opacity brushes, test C program and one output image. The output image (test.png) is the result of;

   ./testbrush -brush brush_op10.png -output test.png -blend

Basically it draws a brushed line using a 10% opaque brush. It also copies the brush into the image so you can see how it looks alone. Checkout the ends of the line and you'll see the issue. I would expect (or was hoping) that the whole line would be a uniform thick line, a blended version of the brush and the black background. Kinda like you'd see with a paint brush tool in Gimp. That's not the case, the resulting line far more opaque than I would expect. I imagine pixels are getting set and blended over and over. The ends of the line are closer to the appearance I would expect.

Steve

>>> Pierre <[email protected]> 07/07/07 6:33 AM >>>
Hi Steve,

On 7/6/07, Steve Lime <[email protected]> wrote:
> Hi all: This one has got me stumped and I hope I'm missing something obvious. I have brushes with variable transparency in the alpha channel. This gives a softer edge when drawing a wide line. Works terrific is blending is enabled. If blending isn't enabled I was hoping the result would be a wide line with variable variable transparency (e.g. opaque center and progressively transparent pixels towards the edge).  I've attached samples. You can see what the brush looks like at the end of the line in the no blending image. Any hope?

Can you put a link to the image and code? It looks like the list
filtered the attachments.

Cheers,
--Pierre