Files
test/source/blender/imbuf
Aras Pranckevicius 1e0bf33b00 ImBuf: optimize IMB_transform
IMB_transform is used by Sequencer (and other places) to do image
translation/rotation/scale on the CPU. This PR speeds up parts of it,
particularly when bilinear filtering is used. No behavior changes are
expected.

- Don't use virtual function calls inside inner loop. The code was using
  class hierarchies with virtual calls just to do equivalent of "outside
  of image? ignore" and "wrap UV coordinates or not?" decisions. Make those
  use non-virtual function based code.
- Simplify pixel sampling functions to only do the work as needed by
  anything within Blender codebase. For example, bilinear sampling of uchar
  images always uses 4 RGBA channels and never does "UV wrap" logic.
- Bilinear interpolation uchar: completely branchless SIMD code now.
- Bilinear interpolation float: 2x floor() calls instead of 4x floor() +
  2x ceil(), and final sample blending is done with SIMD.

Sequencer at 4K UHD resolution, with two image strips that need a transform,
playback framerate:

- Windows Ryzen 5950X: 18.7fps -> 26.2fps (IMB_transform time per frame goes
  26.3ms -> 11.2ms)
- Mac M1 Max: 27.3fps -> 31.4fps

At that point the IMB_transform is not the slowest part of where playback
takes time (but rather sequencer effect application etc.).

Note: the amount of _actual code_ got a bit smaller. But I've added 100 lines
of unit tests in BLI_math_interp_test.cc, the bilinear interpolation
functions were only tested very indirectly by CPU compositor template
image tests.

Pull Request: https://projects.blender.org/blender/blender/pulls/115653
2023-12-14 15:10:30 +01:00
..
2023-12-14 15:10:30 +01:00
2023-12-14 15:10:30 +01:00

The following 4 steps to adding a new image format to blender, its
probably easiest to look at the png code for a clean clear example,
animation formats are a bit more complicated but very similar:

Step 1:
create a new file named after the format for example lets say we were
creating an openexr read/writer  use openexr.c
It should contain functions to match the following prototypes:

struct ImBuf *imb_loadopenexr(unsigned char *mem,int size,int flags);
/* Use one of the following depending on what's easier for your file format */
short imb_saveopenexr(struct ImBuf *ibuf, FILE myfile, int flags);
short imb_saveopenexr(struct ImBuf *ibuf, char *myfile, int flags);

/* Used to test if its the correct format
int IMB_is_openexr(void *buf);

Step 2:
Add your hooks to read and write the image format these go in
	writeimage.c and readimage.c  just look at how the others are done

Step 3:
Add in IS_openexr to blender/source/blender/imbuf/IMB_imbuf_types.h
Add in R_openexr to source/blender/makesdna/DNA_scene_types.h

Step 4:
Add your hooks to the gui.
source/blender/src/buttons_scene.c
source/blender/src/toets.c
source/blender/src/writeimage.c

Step 5:
edit the following files:
blender/source/blender/imbuf/intern/util.c
blender/source/blender/src/filesel.c
blender/source/blender/src/screendump.c
and add your extension so that your format gets recognized in the thumbnails.

Step 6:
Alter the build process:
For cmake you need to edit blender/source/blender/imbuf/CMakeLists.txt
and add in your additional files to source_files.
If you have any external library info you will also need to add that
to the various build processes.

Step 7:
Its also good to add your image format to:
makepicstring in blender/source/blender/blenkernel/intern/image.c