Hi Patrice,

On Sat, Mar 1, 2008 at 12:39 PM, Patrice Poly wrote:

Hello

I have searched a lot about this, and couldn't find anything apart a few lines in an old summer of code page, and in this old webpage : http://www.re.org/tom/computer/gimp/index.html#preview unfortunately this patch only applies to 2.3

this is why I allow myself to post here as a feature wish, even though I am absolutely not a coder.

I am using GIMP every single day for my 3D texturing work, and i have to blend together parts of photographies in an interactive way. Parts need to be lined accurately so that you don't create blur in the blending areas.
( someone told me Hugin does it perfectly, but at a first glance, it seems to involve complex settings and a lot of click work before it computes a solution, when you just need to move things on the fly and see how it goes . Hugin seems to be more suitable for assembling large images together than a lot of little parts )

As GIMP is now, you need to move/scale/rotate/shear/perspective a selection or a layer, apply transformation, check if it lines good, undo, transform again, check, etc, because the preview always turn to totally opaque , whatever the layer opacity is.

Having a little slider to set the preview mode/transparency would be a real enhancement for this kind of workflow. Another clean solution would be that the preview simply follows the active layer mode/opacity .

In order to have a genuinely clean solution, I believe that GEGL needs to be integrated for layer compositing. Because the main issue here is that, when you overlay an preview of N opacity over a layer of N opacity, the appearance is that of

N opacity -- ie. such a preview is still not accurate. It's the same effect that occurs when you draw a dab of paint at 50% opacity and then draw another over the top -- the result is more than 50% opaque.

What needs to happen is, the preview is composited onto the layer with 100% opacity, before that layer is composited onto the one below. This is rather tricky and without a graph-based image display, it is difficult to do in a non-kludgey way.

I have read about Iwarp as a tool, that combined with a transparent transform preview would turn GIMP into a fantastic texturing tool.

I have no clue how difficult it can be to code this, but I hope the developers of GIMP can find an interest in this.

With all my thanks for all the work done,

regards

patrice poly