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why would the input png automatically get blurred?

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why would the input png automatically get blurred?

oneaty
The xcf should reproduce the issue. Just delete the existing layer from
layer->delete layer, and then file->open as layers to import the attached png
file, and you will see the figure gets blurred. Quite weird, is it?

Also another question is, what's the use of "new from visible"? It seems it
carries the figure information to the new layer, if so, why not directly work on
the figure layer itself?

Attachments:
* http://www.gimpusers.com/system/attachments/516/original/fermisurface_blur_debug.xcf
* http://www.gimpusers.com/system/attachments/517/original/Fermichangeb.png

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Re: why would the input png automatically get blurred?

Michael Schumacher
On 03/15/2017 08:10 PM, bsmile wrote:

> The xcf should reproduce the issue. Just delete the existing layer from
> layer->delete layer, and then file->open as layers to import the attached png
> file, and you will see the figure gets blurred. Quite weird, is it?

The image is in indexed colors mode. Use Image > Mode to switch to RGB.

> Also another question is, what's the use of "new from visible"? It seems it
> carries the figure information to the new layer, if so, why not directly work on
> the figure layer itself?

It is a very fast way to create a new layer from exactly what's visible
in the image as a whole. This is useful if you want to reuse the current
result in another image, for example.


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why would the input png automatically get blurred?

oneaty
>The image is in indexed colors mode. Use Image > Mode to switch to
>RGB.
>It is a very fast way to create a new layer from exactly what's
>visible
>in the image as a whole. This is useful if you want to reuse the
>current
>result in another image, for example.


Thanks, after change the mode, the figure can be corrected loaded. Can you
please explain why? This surely helps quickly understand gimp.


I actually want to make use the old xcf to work for a new figure by replacing
the underlying figure. But it seems when I turned the eye on the visible layer,
the old figure shows up. I am here upload both the xcf file and the intended
figure, can you help me with that?


Thanks!

Attachments:
* http://www.gimpusers.com/system/attachments/518/original/fermisurface_b.xcf
* http://www.gimpusers.com/system/attachments/519/original/Fermichangeb.png

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Re: why would the input png automatically get blurred?

Ofnuts-2
On 15/03/17 21:14, bsmile wrote:

>> The image is in indexed colors mode. Use Image > Mode to switch to
>> RGB.
>> It is a very fast way to create a new layer from exactly what's
>> visible
>> in the image as a whole. This is useful if you want to reuse the
>> current
>> result in another image, for example.
>
> Thanks, after change the mode, the figure can be corrected loaded. Can you
> please explain why? This surely helps quickly understand gimp.
>

In indexed mode, the color of a pixel in the image (in all layers) is
taken from a "color map". Since the index in the color map is a 8-bit
byte, you can only have 256 colors (across all layers). When you import
another image, its colors are approximated with the 256 colors in the
current colormap. The first victims of this color shortage are the
anti-aliasing pixels along the edges of things that are a blend of the
two colors in various (and numerous) proportions(*) and the edges become
jagged.

(*) Experiment: Take a blank image, add a black text layer, and merge it
down to obtain one single layer with black text over white. Then Go to
Colors>Info>Color cubes analysis.  You will find much more than two
colors... these are the 250 shades of grays used in the edge pixels. You
can start Color>Posterize and see what happend to the text outline when
you reduce the number of colors.
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why would the input png automatically get blurred?

oneaty
>In indexed mode, the color of a pixel in the image (in all layers) is
>taken from a "color map". Since the index in the color map is a 8-bit
>byte, you can only have 256 colors (across all layers). When you
>import
>another image, its colors are approximated with the 256 colors in the
>current colormap. The first victims of this color shortage are the
>anti-aliasing pixels along the edges of things that are a blend of the
>two colors in various (and numerous) proportions(*) and the edges
>become
>jagged.
>
>(*) Experiment: Take a blank image, add a black text layer, and merge
>it
>down to obtain one single layer with black text over white. Then Go to
>Colors>Info>Color cubes analysis.  You will find much more than two
>colors... these are the 250 shades of grays used in the edge pixels.
>You
>can start Color>Posterize and see what happend to the text outline
>when
>you reduce the number of colors.

Thanks, yes, I did the experiment and I saw the change now.

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