indexed color

[gimp-artist]

I loaded an image with RGB mode. I made a palette from the image. I also made a brush preset with a color in the palette just I created.

Then, I changed the mode to indexed mode for the image I'm working on. When I drew with the preset brush just I created, the color look different in the indexed image. The brush color I chose was originally from the image so I think the color should be the same whether it is on RGB or indexed mode.

Why is that so? I adjusted the opacity to make them look the same, but there is no way to make it work since the indexed brush color is way more clean.

[dinasset]

If you want to see/use the same colours the sequence should be:
- convert to indexed
- convert back to RGB
- create the palette
- create the brush

[Blighty]

(05-01-2018, 02:25 AM)gimp-artist Wrote: I loaded an image with RGB mode. I made a palette from the image. I also made a brush preset with a color in the palette just I created.

Then, I changed the mode to indexed mode for the image I'm working on. When I drew with the preset brush just I created, the color look different in the indexed image. The brush color I chose was originally from the image so I think the color should be the same whether it is on RGB or indexed mode.

Why is that so? I adjusted the opacity to make them look the same, but there is no way to make it work since the indexed brush color is way more clean.

An rgb image has many colours - up to 16 million.
An indexed image has a max of 256 colours.
When you convert from rgb to indexed the number of colours get reduced.

What happend in your case.
You made a palette from rgb and selected a brush colour from that.
Then you converted to indexed. Reduced the number of colours. The brush colour you selected was no longer in the indexed colour map. So another colour from the colour map was used - slightly different from your selected brush colour.

dinasset's method is the correct way to do this.

[gimp-artist]

(05-01-2018, 07:30 AM)Blighty Wrote:

(05-01-2018, 02:25 AM)gimp-artist Wrote: I loaded an image with RGB mode. I made a palette from the image. I also made a brush preset with a color in the palette just I created.

Then, I changed the mode to indexed mode for the image I'm working on. When I drew with the preset brush just I created, the color look different in the indexed image. The brush color I chose was originally from the image so I think the color should be the same whether it is on RGB or indexed mode.

Why is that so? I adjusted the opacity to make them look the same, but there is no way to make it work since the indexed brush color is way more clean.

An rgb image has many colours - up to 16 million.
An indexed image has a max of 256 colours.
When you convert from rgb to indexed the number of colours get reduced.

What happend in your case.
You made a palette from rgb and selected a brush colour from that.
Then you converted to indexed. Reduced the number of colours. The brush colour you selected was no longer in the indexed colour map. So another colour from the colour map was used - slightly different from your selected brush colour.

dinasset's method is the correct way to do this.

I understand that the indexed image has only 256 colors maximum. I thought I tested an image with less than 256 colors, but maybe it is not. Then the colors are more than 256 for the result as you said. Right? Then how do I know how many colors my image has?

(edited: please answer below the frame of the quote)

[Ofnuts]

Finding color for the palette and finding colors for the color-indexing have different criteria (say, widest color coverage for the palette, and best visual appearance given dithering for the color-indexing). There is no guaranteed that they will be the same, color indexing isn't just creating a palette from the image and using it for indexing.