Files
test/source/blender/imbuf
Aras Pranckevicius f16dbd0360 ImBuf: no need to use double precision inside IMB_transform
Double precision pixel coordinate interpolation was added in 3a65d2f591 to
fix an issue of "wobbly" resulting image at very high scale factors. But
the root cause of that was the fact that the scanline loop was repeatedly
adding the floating point step for each pixel, instead of doing multiplication
by pixel index (repeated floating point additions can "drift" due to
imprecision, whereas multiplications are much more accurate).

Change all that math back to use single precision floats. I checked the
original issue the commit was fixing, it is still fine. Also added a gtest
to cover this situation: `imbuf_transform, nearest_very_large_scale`

This makes `IMB_transform` a tiny bit faster, on Windows/VS2022/Ryzen5950X
scaling an image at 4K resolution:
- Bilinear: 5.92 -> 5.83 ms
- Subsampled3x3: 53.6 -> 52.7 ms

Pull Request: https://projects.blender.org/blender/blender/pulls/117160
2024-01-16 13:32:47 +01:00
..
2024-01-10 08:56:25 +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