Page 1 of 1
transparent GIF problem
Posted: Mon Dec 05, 2005 2:48 pm
by mindplay
I'm trying to generate a transparent GIF with GFLax in ASP, but I've run into a problem. Let's say I do this:
Code: Select all
<%
Const AX_GIF = 2
Const AX_To8Colors = 8
Const AX_NoDither = 0
Const AX_ToColors = 0
BG = RGB(255,255,255)
FG = RGB(255,0,0)
Text = "This is a test"
Set Pic = Server.CreateObject("GflAx.GflAx")
Pic.EnableLZW = True
Pic.FontName = "Verdana"
Pic.FontSize = 36
W = Pic.GetTextWidth(Text)
H = Pic.GetTextHeight(Text)
Pic.NewBitmap W, H, BG
Pic.TextOut Text, 0, 0, FG
Pic.SaveFormat = AX_GIF
Pic.ChangeColorDepth AX_To8Colors, AX_NoDither, AX_ToColors
Pic.UseTransparency = True
Pic.MaskColor = Pic.GetColorAt(0,0)
Pic.SaveBitmap Server.MapPath("test.gif")
%>
<HTML>
<HEAD></HEAD>
<BODY><IMG SRC="test.gif"></BODY>
</HTML>
... as you can see, the red color is masked out as transparent, but the color at (0,0) is white. I've checked that GetColorAt(0,0) returns FFFFFF - this is true. I also tried RGB(255,255,255) which gives the same result ... so the error must lie within the transparency/maskcolor/savebitmap functions?
Posted: Wed Dec 07, 2005 1:08 pm
by mindplay
Anybody else experienced this problem? Anyone know the cause, or know if there's any way to work around it?
Posted: Wed Dec 07, 2005 8:24 pm
by xnview
mindplay wrote:Anybody else experienced this problem? Anyone know the cause, or know if there's any way to work around it?
Ok, the problem is antialias!
Perhaps by adding a FontAntialias property will fixed the problem!
Posted: Thu Dec 08, 2005 8:35 am
by mindplay
I don't see how that could be the problem? it shouldn't matter what's in the image in the first place - since I convert it to 8 colours first, the image has a palette ... normally, when you create a transparent GIF, that's what you do - reduce to x number of colors, then pick the color you want to be transparent.
If I set a specific MaskColor, shouldn't it mask that color out? otherwise what's the point of having MaskColor? setting it doesn't seem to have any effect at all?
Posted: Thu Dec 08, 2005 10:27 am
by xnview
mindplay wrote:I don't see how that could be the problem? it shouldn't matter what's in the image in the first place - since I convert it to 8 colours first, the image has a palette ... normally, when you create a transparent GIF, that's what you do - reduce to x number of colors, then pick the color you want to be transparent.
If I set a specific MaskColor, shouldn't it mask that color out? otherwise what's the point of having MaskColor? setting it doesn't seem to have any effect at all?
But here you have not a text in red, zoom in...
Posted: Thu Dec 08, 2005 12:23 pm
by mindplay
Yes, the edge pixels are not full-intensity red - I also don't want those masked out, so that's not a problem. But look at the code:
Pic.MaskColor = Pic.GetColorAt(0,0)
The color at 0,0 is the background color, WHITE, FFFFFF ... not red.
So white should be masked out - not red.
But it doesn't seem to matter WHAT I set MaskColor to - white OR red, it always masks out the same thing ... this property doesn't seem to have any effect at all?
Posted: Thu Dec 08, 2005 2:15 pm
by xnview
mindplay wrote:Yes, the edge pixels are not full-intensity red - I also don't want those masked out, so that's not a problem. But look at the code:
Pic.MaskColor = Pic.GetColorAt(0,0)
The color at 0,0 is the background color, WHITE, FFFFFF ... not red.
So white should be masked out - not red.
But it doesn't seem to matter WHAT I set MaskColor to - white OR red, it always masks out the same thing ... this property doesn't seem to have any effect at all?
Ok, right. Send me your a PM with your email, and i'll send you a beta version.