Another GEM question... (somehow, no matter how much of GEM I learned, there is always something that you'd think would be straightforward, but isn't...)

I would like to construct a rectangular mask for an image. The mask should have a black background (suppress the pixels outside of the rectangle) with a white rectangle somewhere inside (eventually, I'd like to be able to position the rectangle using [translateXYZ]).

I have an example from awhile ago of [pix-snap]ping a shape into a pix_buffer, and then using the pix_buffer data for further processing. So I tried to apply the same logic to this problem:

• One [gemhead] draws the square, pix_snap, pix_buffer_write.
• The main [gemhead] does [t a a]
  • Right-hand (first) does pix_buffer_read
  • Left-hand (second) is pix_image, pix_mask, pix_texture, square

If I connect pix_buffer_read directly to pix_texture, then I see the mask as I expect.

Then the trouble begins -- I connect pix_buffer_read to pix_mask's right inlet, and... Pd hangs. I have to force quit.

1. Is there another way to do this that will not crash?
2. Is this just a bug? Or am I doing something wrong?

hjh

For the special case of a rectangle, I think I can work around it using pix_sig2pix. I just got a prototype to work; I'll work on the positioning next.

The working prototype also demonstrates that [pix_mask] isn't fundamentally broken -- it just doesn't like it when the mask image comes from pix_snap.

It would be nice to have a general solution, to make it easy to substitute a circle in place of the rectangular mask.

hjh

The eventual finding is: pix_resize doesn't work well for downsizing large image files. It's better to pre-size images to fit the need.

No hang if I put in a 500x500 image.

Hang, if I put in a 2000x1500 image.

hjh

I didn't test anything, but pix crop comes into my mind...