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Transparency coloured when exporting image

Jul 11, 2011, 19:58
Post: #1
Transparency coloured when exporting image
Hello,

You probably think "but come on, there are many places where this is explained...". And so it is, but it doesn't work anyways.

I have an image with transparent areas. I have an alpha channel. When I save the file, I do use the "Save colour values from transparent pixels" for png and for gif I check "Interlace" option.

I have done the rigth click -> colour to alpha. What happens when I do this is that some white parts become black.

Things I have noted, perhaps that doesn't matter , is that when checking the alpha channel in the layer tool, it is white and not transparent.

The image is attached.

One last thing, I did copy the image from ConeptDraw (visio-alike application on Mac) before trying to save it with transparency.

This is driving me nuts, I have struggled for hours. I have done it before (way back), but something is different now.

Thanks in advance!


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Jul 11, 2011, 20:35
Post: #2
RE: Transparency coloured when exporting image
(Jul 11, 2011 19:58)Nicsoft Wrote:  Hello,

You probably think "but come on, there are many places where this is explained...". And so it is, but it doesn't work anyways.
Well, since you aren't too explicit on what "this" is...

(Jul 11, 2011 19:58)Nicsoft Wrote:  I have an image with transparent areas. I have an alpha channel. When I save the file, I do use the "Save colour values from transparent pixels" for png and for gif I check "Interlace" option.
OK

(Jul 11, 2011 19:58)Nicsoft Wrote:  I have done the rigth click -> colour to alpha. What happens when I do this is that some white parts become black.
I don't see any black in your pic. Most of the transparent area would be white if not transparent (sat=0%, value>95%). Maybe having both before and after pictures would help.

(Jul 11, 2011 19:58)Nicsoft Wrote:  Things I have noted, perhaps that doesn't matter , is that when checking the alpha channel in the layer tool, it is white and not transparent.
An alpha channel is white where the picture is opaque, and black were it is transparent (grays indicate partial transparency). I don't see anything special there.

(Jul 11, 2011 19:58)Nicsoft Wrote:  One last thing, I did copy the image from ConeptDraw (visio-alike application on Mac) before trying to save it with transparency.
Not relevant IMHO (but you should use Dia Smile )

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Jul 12, 2011, 05:31 (This post was last modified: Jul 12, 2011 05:32 by Nicsoft.)
Post: #3
RE: Transparency coloured when exporting image
Hi ofnuts.

Thank's for your reply!

(Jul 11, 2011 20:35)ofnuts Wrote:  
(Jul 11, 2011 19:58)Nicsoft Wrote:  Hello,

You probably think "but come on, there are many places where this is explained...". And so it is, but it doesn't work anyways.

Well, since you aren't too explicit on what "this" is...
Actually, I woke up this night realising I didn't write what the problem was about...

The problem is that when I use the image in a web page I am creating, the area I want to be transparent is white. In Gimp, this area is marked as transparent.

(Jul 11, 2011 20:35)ofnuts Wrote:  
(Jul 11, 2011 19:58)Nicsoft Wrote:  I have done the rigth click -> colour to alpha. What happens when I do this is that some white parts become black.
I don't see any black in your pic. Most of the transparent area would be white if not transparent (sat=0%, value>95%). Maybe having both before and after pictures would help.

Sat is ok I think (see included image for configuration).

   

I'm not sure about value, where do I specify this?

And now I understand the funktion colour to alpha better. Of course, the transparent colour doesn't have any "colour" that I can make transparent...

(Jul 11, 2011 20:35)ofnuts Wrote:  
(Jul 11, 2011 19:58)Nicsoft Wrote:  Things I have noted, perhaps that doesn't matter , is that when checking the alpha channel in the layer tool, it is white and not transparent.
An alpha channel is white where the picture is opaque, and black were it is transparent (grays indicate partial transparency). I don't see anything special there.

Ok. Actually, the image itself is white and the transparent area is black. But still, on the webpage the transparent area is coloured white. But still again, the area is marked transparent in Gimp.

(Jul 11, 2011 20:35)ofnuts Wrote:  
(Jul 11, 2011 19:58)Nicsoft Wrote:  One last thing, I did copy the image from ConeptDraw (visio-alike application on Mac) before trying to save it with transparency.
Not relevant IMHO (but you should use Dia Smile )

Done that quite a bit, but the company paid for this so... Smile


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Jul 12, 2011, 08:18
Post: #4
RE: Transparency coloured when exporting image
(Jul 12, 2011 05:31)Nicsoft Wrote:  The problem is that when I use the image in a web page I am creating, the area I want to be transparent is white. In Gimp, this area is marked as transparent.
How is the "web site" managed? There are web sites that do not support transparency in images (Facebook pages, for instance, IIRC). Check that the web site is displaying an unchanged version of your image: in the web site, "save image as", and compare with your original image.

(Jul 12, 2011 05:31)Nicsoft Wrote:  Sat is ok I think (see included image for configuration).
I'm not sure about value, where do I specify this?
Wrong dialog... This is a dialog to change saturation acros the image/selection. If you want to see pixels values, use the "Pointer" dialog in Windows/Dockable dialogs. Pixels components can be expressed as RGBA, but also as HSV (see http://en.wikipedia.org/wiki/HSL_and_HSV).

(Jul 12, 2011 05:31)Nicsoft Wrote:  Ok. Actually, the image itself is white and the transparent area is black. But still, on the webpage the transparent area is coloured white. But still again, the area is marked transparent in Gimp.
This makes me all the more suspicious that the web site support is playing tricks with your image.

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Jul 12, 2011, 08:51
Post: #5
RE: Transparency coloured when exporting image
Appearently, I don't really suck at this after all. The image is fine and works as it should be. What I do suck in is web-development. I used the image in an <button>-tag and, of cours, the button itself is decorated with backgroud and border. So the image is perfekt, I saw the background of the button through transparent areas.

Thank's for the time and sorry for bothering!
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Jul 12, 2011, 10:18
Post: #6
RE: Transparency coloured when exporting image
No worries...

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