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.

Regards,
Michael
GPG: 96A8 B38A 728A 577D 724D 60E5 F855 53EC B36D 4CDD

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.