On Sun, May 23, 2021 at 1:23 PM Thomas Schmitt <scdbac...@gmx.net> wrote:
> Hi,
>
> i wrote:
> > > halve_jpeg.c
>
> Dan Hitt wrote:
> > It was unwilling to deal with a non-color image that i had ("Unsuitable
> JPEG
> > format with 1 components per pixel"), [...]
> > if i need to deal with non-color images, i can try to modify it.
>
> It is much ad-hoc work, i have to confess. The images which made my
> computer
> mad came from a professional camera and all were in 3 colors.
>
> Every occurence of 3 between "2013" and "if(argc < 3)" would have to
> become hjpg->cinfo_in.output_components.
>
> Next problem is the hardcoded
> cinfo_out->in_color_space= JCS_RGB;
> which must become hjpg->cinfo_in.out_color_space.
>
> Another need for change might come from the program's habit to size down
> to half edge length by default.
> (Originally this was its only mode because it was only intended to make
> the image size digestible for ImageMagick "convert". Then i got carried
> away and implemented more flexible scaling.)
>
> -------------------------------------------------------------------------
>
> I forked a new program reformat_jpeg.c and implemented those changes.
> It seems to work with grayscale
>
> https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Nine_steps_stair_in_Lysekil_-_bw.jpg/800px-Nine_steps_stair_in_Lysekil_-_bw.jpg
> and with the color images i tested up to now.
> (Ye olde halve_jpeg got lots of testing during the years.)
>
> Download:
> http://scdbackup.sourceforge.net/reformat_jpeg.c
> (if sourceforge gets over its 503 and 504 errors of today)
> SHA256:
> 64ab46e8102e304558f0a10c85cc2dd08010d4346c50ab4eca678049d2b9c260
>
> Compilation:
> cc -g -Wall -o reformat_jpeg reformat_jpeg.c -ljpeg
>
> Usage is like with halve_jpeg, except the size default.
>
>
> Have a nice day :)
>
> Thomas
>
>
Thanks Thomas!
The reformat_jpeg program compiles and runs quickly, and also deals with my
non-color images (which i visually checked with qiv). Thank you so much
for sharing the fruit of your labor! :)
dan
