Coloring line drawing problem

[sl60]

   
I've been experimenting with coloring a line drawing. A made a quick sample shingle roof, imported it as a TIF into Gimp. The lines were pretty gray so I needed them darker. Erode didn't give me the results I wanted so, I used Select By Color and darkened the lines. I wanted to color in the tiles individually so I took a small sample, colored it all  a darker gray color with the intention of returning to make a few of the shingles a lighter value. But adding the color had the effect of "erasing" the lines defining the individual shingles so when I tried to color a single tile the lighter color the whole thing turned the lighter color.

How can I set this up to keep the line art and color individual shingles?

[rich2005]

Your image does not really show anything. If that is what you are using, throw it away and start again. Make an out-line drawing on a transparent layer.

For colouring in line drawings the most recent Gimp 2.10.14 & later comes with a  bucket fill - line art option  If not in your version of Gimp it is worth updating. Otherwise it is individual selections and fills.

Do not try and fill in a single layer, you can do that but it makes correcting errors that bit harder. The bucket fill - line art is quite good at finding boundaries but not perfect. You might need the occasional correction.

Up to you to find suitable patterns for the bucket fill, If some are semi-transparent, another layer for a general fill is used.

   

[sl60]

using 2.10.

I need to work with an imported line drawing of shingles and I want to color them with various shades of gray. The image I used is fine except that it imports with some black lines and some gray, even though it is black-and-white.

[rich2005]

Quote:using 2.10.

Just a note to anyone reading this. It is important to give all information. If your forum profile says gimp 2.8 expect replies based on Gimp 2.8
Gimp 2.10 has evolved and the latest version does have some extra features than earlier versions. Please give the whole version number. Easy to determine, the Gimp menu Help -> About will tell you.

Quote:I need to work with an imported line drawing of shingles and I want to color them with various shades of gray. The image I used is fine except that it imports with some black lines and some gray, even though it is black-and-white.

   

Always difficult to give advice with a jpeg screenshot of what must be a larger image. I can see that there is some transparency there but it is not black  and white. Black is not black (percentages not zero) and the line is a grey.  With an image like that, fuzzy select / colour select even with zero threshold only gives a partial selection.  A colour erase brush takes out part of the line as well, as does color-to-alpha. 

If you want to paint in various shades of grey, keeping the 'lines' then you need just the lines on transparency and just-my-opinion, the easiest way is re-create on a new layer painting in the lines. Then colour under that. Of course you can always go in at a pixel level on a single layer and paint each area individually.

Whatever happened to making a tiles pattern? as https://www.gimp-forum.net/Thread-Roof-tiles

[rich2005]

This just my way of attacking the problem

ref:  https://i.imgur.com/B6Wp8mG.jpg

Using your posted image as a template it only takes  2 or 3 minutes to paint in (pencil tool, 1 pixel brush) the line-work . That can be duplicated, spread out as layers and each layer 'randomised' a bit using Layer -> Transform -> Offset Not difficult (1), that only takes 2 or 3 minutes as well. That leaves an image with lines on transparency that is used as a repeatable pattern in a larger canvas (2). That image attached as an example. (a gimp xcf.gz - opens straight up in Gimp)

ref:  https://i.imgur.com/HSLdXi1.jpg

Colouring in? There will be any number of ways, The important bit is use a layer under the line drawing It really will save you when you make a mistake.   A bit of experimenting and this sequence worked for me. 
Fill the layer with simplex noise  Filters -> Render -> Noise -> Simplex Noise (3) 
Maybe go straight to Gaussian blur or an intermediate Filters -> Blur -> Pixelize (4)
Now to even the fill a small Gaussian blur Filters -> Blur -> Gaussian Blur (5)

[sl60]

(06-05-2020, 08:14 AM)rich2005 Wrote:

Quote:using 2.10.

Just a note to anyone reading this. It is important to give all information. If your forum profile says gimp 2.8 expect replies based on Gimp 2.8
Gimp 2.10 has evolved and the latest version does have some extra features than earlier versions. Please give the whole version number. Easy to determine, the Gimp menu Help -> About will tell you.

Quote:I need to work with an imported line drawing of shingles and I want to color them with various shades of gray. The image I used is fine except that it imports with some black lines and some gray, even though it is black-and-white.

Always difficult to give advice with a jpeg screenshot of what must be a larger image. I can see that there is some transparency there but it is not black  and white. Black is not black (percentages not zero) and the line is a grey.  With an image like that, fuzzy select / colour select even with zero threshold only gives a partial selection.  A colour erase brush takes out part of the line as well, as does color-to-alpha. 

If you want to paint in various shades of grey, keeping the 'lines' then you need just the lines on transparency and just-my-opinion, the easiest way is re-create on a new layer painting in the lines. Then colour under that. Of course you can always go in at a pixel level on a single layer and paint each area individually.

Whatever happened to making a tiles pattern? as https://www.gimp-forum.net/Thread-Roof-tiles

Thanks. if you'll re-read my original post you'll understand that I'm coloring in the black-and-white shingles, not creating a line drawing.

---

   
Here is a part of the original line drawing png that needs to be colored in shades of grays. The lines need to be darkened and made more solid.

[Ofnuts]

On an image like this with dark lines on a white backrgound,

• to color the lines, you can paint after setting the tool to Lighten only mode. Since white is lighter than anything else, the white remains white. An equivalent way is to add a layer above this, set  it to  Lighten only mode, and paint on it in Normal mode.
  

   

• likewise to color the backrground, you set the mode to Darken only:
  

   

In the general  case, though, you would transform your image into lines over transparent background by using Color>Color to alpha, and either paint the lines after alpha-locking the layer, or paint a background using Behind mode (or another layer under your lines). This will preserve the smooth edges of the lines.