Re: [Gimp-user] Opacity Layers?

2004-04-15 Thread Steve Stavropoulos
On Fri, 9 Apr 2004, David Wright wrote:

> Does the gimp support opacity layers? By opacity layer I mean an layer 
> with a 8-bit numer for each pixel, where instead of being intrepreted as 
> a gray or color intensity value, the number is intrepreted as a pure 
> opacity. When it is 255, the pixel is black; when it is 0, the pixel 
> below shows through perfectly; when it is intermediate, the pixel is an 
> appropriate average of black and the color of the pixel below.
> 

 What you want to create is a layer with the alpha channel representing 
your image and a solid color (black or white in your case).
 Simple steps:
1) Create a new white layer
2) Add layer mask (Black, full transparency)
3) select the layer with your text and in the image press ctrl-a and 
ctrl-c to select all and copy the image.
4) Select the layer mask in the layers dialog and in the image press 
ctrl-v to paste.
5) Anchor layer
6) The layer you just created is what you want. (you may like to right 
click in the layer and "Apply layer mask")

 I just confirmed these steps in my gimp 1.2.1 but I think there isn't any 
difference in gimp 2.0.x.

PS. If you want to use this image in a web page notice that IE doesn't 
support 8-bit transparent pngs. (there are some workarounds that you can 
find in the archives of this list, but nobody should care about IE :P)

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Re: [Gimp-user] Opacity Layers?

2004-04-09 Thread Michael Schumacher
David Wright wrote:
Does the gimp support opacity layers? By opacity layer I mean an layer 
with a 8-bit numer for each pixel, where instead of being intrepreted as 
a gray or color intensity value, the number is intrepreted as a pure 
opacity. When it is 255, the pixel is black; when it is 0, the pixel 
below shows through perfectly; when it is intermediate, the pixel is an 
appropriate average of black and the color of the pixel below.

Assuming such a layer exists, how can I transform a grayscale layer into 
an opacity layer?
This sounds like you want layer masks or layer modes. But you probably 
won't need them here.

This problem arises because I have scanned penciled text on white paper 
into a single-layer grayscale image. I want to use the gimp to make that 
text appear over another image. I have already tried (1) making a single 
color transparent and (2) using the magic wand to "partially" select the 
text. These solutions all have the problem that some of the color of the 
original background "leaks" into the final image near the text. That's 
why I want to use the intensity values of the original purely to measure 
opacity, not to communicate any color information at all. How can I do 
this?
Try Filters->Colors->Color To Alpha

HTH,
Michael
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[Gimp-user] Opacity Layers?

2004-04-09 Thread David Wright
Does the gimp support opacity layers? By opacity layer I mean an layer 
with a 8-bit numer for each pixel, where instead of being intrepreted as 
a gray or color intensity value, the number is intrepreted as a pure 
opacity. When it is 255, the pixel is black; when it is 0, the pixel 
below shows through perfectly; when it is intermediate, the pixel is an 
appropriate average of black and the color of the pixel below.

Assuming such a layer exists, how can I transform a grayscale layer into 
an opacity layer?

This problem arises because I have scanned penciled text on white paper 
into a single-layer grayscale image. I want to use the gimp to make that 
text appear over another image. I have already tried (1) making a single 
color transparent and (2) using the magic wand to "partially" select the 
text. These solutions all have the problem that some of the color of the 
original background "leaks" into the final image near the text. That's 
why I want to use the intensity values of the original purely to measure 
opacity, not to communicate any color information at all. How can I do this?

I did google on this, but wasn't able to find a solution. Please help if 
you can. Thanks!

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