Archive for April, 2008

OpenGTL 0.9.2 and linear RGB color space

29 April, 2008 1 comment

I finally made a new release of OpenGTL, with a nearly full support of the CTL (Color Transformation Language) syntax. While large part of the standard library is still unavailable, it has all the features currently needed for Krita’s color spaces.

This allows to bring color management to color spaces that didn’t have that, and most specifically our RGB HDR (High-Dynamic Range) color spaces. It is especially interesting, because we need to have both a linear color space (for most high dynamic range operations, and if you want to do gamma correct scaling) and a non linear (a sRGB color space, which is used for color conversion, mostly with the painterly framework). So we were in need to be able to have profiles on top of those color spaces, and that is exactly what CTL is giving to us.

Back to gamma correct scaling, some times ago someone mentioned to me this link, scaling with non-linear color space gives a wrong result. Before we started using CTL based RGB color space, our HDR color space were an hybrid of sRGB (non-linear) and scRGB (linear) (don’t try to understand how we got there, I don’t either), and curiously, the scaling was wrong half of the time (don’t try to understand it was possible, I don’t either), but now, using the linear RGB color space, we can have gamma correct scaling:


Drawing assistant : ruler

8 April, 2008 3 comments

Sure you can draw line with the line tool. But I have never felt confortable with that, I think that’s because the resulting line looks too perfect, as you can see on the screenshots below (it’s the top right line).

What I want is to have the virtual version of physical tools (rulers, compas, we can even imagine more fancy stuff). That’s what a drawing assistant is. It controls the drawing on the image, depending on the mouse/stylus movement. So for the ruler drawing assistant, it will force to draw a line. There is a control over the magnetism of the tools, this control how much freedom the artist has, how much the pen can move aside the ruler line.

The second line (starting from the top right), was done using a mouse. The third and fourth with a tablet stylus. The fourth line is here to show an other interest for the drawing assistant, you can control the pressure all over the line.

In fact, I am more interested in a compas tool, but a ruler was more simpler to test the whole framework.