On 8/20/07, Konstantin Svist wrote:

Hi,

I wanted to ask why the lines drawn with a Wacom tablet look so different when drawn in gimp vs. when they're drawn in Photoshop or OpenCanvas.

This has been discussed before (or similar). I don't know the details, but I do know it makes a difference if you use the paintbrush tool versus the pencil tool - might try the other tool and see if that helps. Might also be a linuxwacom issue instead of a gimp issue.

On 8/21/07, Konstantin Svist wrote:

Hi,

I wanted to ask why the lines drawn with a Wacom tablet look so different when drawn in gimp vs. when they're drawn in Photoshop or OpenCanvas.
Attached is an example of lines drawn in Photoshop CS2, CS3, OpenCanvas (sorry, can't remember the version #) and Gimp (2.2.15, I think) The line drawin in Gimp does not look very smooth - there are bumps n the line and it looks segmented.

Why is this happening and is there any way to fix this behavior? Is this intrinsic to Gimp or does it come from the linux wacom driver? Maybe Photoshop/oC have some smoothing algorithms that they apply to raw stroke data..?

a) the pressure curve being used with GIMP is definitely different from the one used by the other software. This is related to the LinuxWacom driver (look up the 'PressCurve' option, to adjust the curve.)
b) yes, oC certainly does have smoothing algorithyms.. and probably Photoshop too.
c) 'p1' seems to be using a different brush than the other 3. d) The 'jumps' in brush size are due to limitations that GIMP places upon brush scaling. There is probably some way to adapt this so it works better for small scale brushes.

Has anyone encountered something similar before?

The ink tool in GIMP is the only tool that currently uses smoothing. As you can see, it produces results comparable to Photoshop and oC:

http://img.photobucket.com/albums/v449/neota/alphazero/ink.png

The smoothing code for the ink tool can probably be adapted for use with normal brush-based paint tools - if you want this, I urge you to investigate.

the way these two tools work is too different, for the adaptation to be possible

to quote Sven : "The paintbrush stamps the brush repeatedly on the canvase to create a brush stroke. The ink tool however calculates the outline of the brush stroke based on geometry and movement of the brush tip. This stroke outline is then filled using a solid color. Both concepts have advantages and disadvantages."

On 8/21/07, David Gowers wrote:

On 8/21/07, Konstantin Svist wrote:

Hi,

I wanted to ask why the lines drawn with a Wacom tablet look so different when drawn in gimp vs. when they're drawn in Photoshop or OpenCanvas.
Attached is an example of lines drawn in Photoshop CS2, CS3, OpenCanvas (sorry, can't remember the version #) and Gimp (2.2.15, I think) The line drawin in Gimp does not look very smooth - there are bumps n the line and it looks segmented.

Why is this happening and is there any way to fix this behavior? Is this intrinsic to Gimp or does it come from the linux wacom driver? Maybe Photoshop/oC have some smoothing algorithms that they apply to raw stroke data..?

a) the pressure curve being used with GIMP is definitely different from the one used by the other software. This is related to the LinuxWacom driver (look up the 'PressCurve' option, to adjust the curve.)
b) yes, oC certainly does have smoothing algorithyms.. and probably Photoshop too.
c) 'p1' seems to be using a different brush than the other 3. d) The 'jumps' in brush size are due to limitations that GIMP places upon brush scaling. There is probably some way to adapt this so it works better for small scale brushes.

Has anyone encountered something similar before?

The ink tool in GIMP is the only tool that currently uses smoothing. As you can see, it produces results comparable to Photoshop and oC:

http://img.photobucket.com/albums/v449/neota/alphazero/ink.png

The smoothing code for the ink tool can probably be adapted for use with normal brush-based paint tools - if you want this, I urge you to investigate.
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On 8/21/07, Jozef Legeny wrote:

the way these two tools work is too different, for the adaptation to be possible

to quote Sven : "The paintbrush stamps the brush repeatedly on the canvase to create a brush stroke. The ink tool however calculates the outline of the brush stroke based on geometry and movement of the brush tip. This stroke outline is then filled using a solid color. Both concepts have advantages and disadvantages."

What you describe is a method of rendering, not a method of smoothing strokes. Understand that stroke smoothing is a strictly mathematical concept -- you know that the user drew through certain locations with a certain pressure, tilt, and speed, and you simplify that set of points into a smoothed stroke (ie. another set of points). Then you render the stroke however is appropriate. To illustrate quite clearly -- Inkscape, a vector drawing program, includes the kind of smoothing I am talking about.

The problems described by Konstantin are a) lack of stroke smoothing
b) lack of smooth rendering of the stroke (mainly, jarring 'jumps' in brush size)

On 8/21/07, Konstantin Svist wrote:

Thanks everyone for advice!
I'll definitely try playing with the pressure curves. And yes, 'p1' was apparently a modified brush (the original artist confirmed it :). But that aside, p2 and o1 look a lot better than g1... I've heard somewhere that gimp was made for photo editing, not drawing/sketching.. so I guess it's not very likely this will change?

I think it's fairly likely. stroke smoothing is useful for photo editing too..

Are there any programs in Linux that were actually made for drawing/sketching?

Krita (which I personally have not had much luck with, i found it crashed a lot)

Thanks!

P.S. just tried the ink tool - it has a fairly annoying "angle" setting which makes the strokes change width based on the angle (angle 0 means horizontal strokes are thin, while vertical strokes are thick). I don't see the same in your example, though - what setting did you change to get that?

If angle 0 means vertical strokes are thick, then you have selected a vertical pen tip. The default pen tip has no orientation, and thus Angle doesn't effect it.
See the 'Shape' section in the ink tool's options. The example image I showed you was done with a circular pen tip, size 3, pressure sensitivity = 1.0. You can manipulate the pen tip using the Shape section (move the box in the diagram)

On Tuesday 21 August 2007, David Gowers wrote:

On 8/21/07, Konstantin Svist wrote:

Thanks everyone for advice!
I'll definitely try playing with the pressure curves. And yes, 'p1' was apparently a modified brush (the original artist confirmed it :). But that aside, p2 and o1 look a lot better than g1... I've heard somewhere that gimp was made for photo editing, not drawing/sketching.. so I guess it's not very likely this will change?

I think it's fairly likely. stroke smoothing is useful for photo editing too..

Are there any programs in Linux that were actually made for drawing/sketching?

Krita (which I personally have not had much luck with, i found it crashed a lot)

Thanks!

The version of Krita I have doesn't crash as before but it runs dead slow. The number of filters and scripts is very limited compared to Gimp. But the CMYK color model was built in from the get go which ultimately will make it a winner for those in publishing.