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JPEG XL: Saving image in float band format fails #2830

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dloebl opened this issue Jun 1, 2022 · 5 comments
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JPEG XL: Saving image in float band format fails #2830

dloebl opened this issue Jun 1, 2022 · 5 comments
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bug
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8.13

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@dloebl
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dloebl commented Jun 1, 2022 •
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jxlsave seems to fail with the following error in case the input image is in the float band format:
jxlsave: error JxlEncoderSetBasicInfo

We noticed this behaviour while resizing images with an alpha channel.

Example image:
test.png

C code:

#include <vips/vips.h>
#include <stdio.h>

int main() {
        VipsImage* in, *thm, *pre, *out;

        VIPS_INIT("test app");

        // load input png
        vips_pngload("test.png",
                &in,
                NULL);

        // resize image
        vips_premultiply(in, &pre, NULL);
        vips_resize(pre, &thm, 0.5, NULL);
        vips_unpremultiply(thm, &out, NULL);

        // save as JPEG XL
        vips_jxlsave(out, "out.jxl", NULL);
        puts(vips_error_buffer());

        vips_shutdown();
        return 0;
}

Environment

  • OS: MacOS 12.4
  • Vips: v8.13 master
  • libjxl: v0.6.1
@dloebl dloebl added the bug label Jun 1, 2022
@jcupitt
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jcupitt commented Jun 1, 2022

Hi @dloebl, you're right, looks like we need to add a new SAVEABLE enum for scRGB. Let's fix this for 8.13.

@jcupitt jcupitt added this to the 8.13 milestone Jun 1, 2022
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jcupitt commented Jun 12, 2022

After asking on libjxl discord, it seems this is the position:

save strategy

  • FLOAT srgb ... convert to 8 bit for write
  • scrgb ... write as float, call JxlColorEncodingSetToLinearSRGB(), libjxl wants 0 - 1 so there's no scaling

load strategy

  • char/short data ... as now
  • float data ... convert to scRGB, attach the profile, no scaling needed, no need to worry about lionear/nonlinear, since libjxl with synthesise a profile with the correct gamma if necessary

jcupitt added a commit that referenced this issue Jun 12, 2022
@jcupitt
fix up scrgb support in JXL
9f3860e 
after some discussion on discord with the libjxl maintainers

see #2830

to do: save scrgb to eg. JPEG fails right now :( we need to do
scRGB->sRGB in jpegsave
@jcupitt
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jcupitt commented Jun 12, 2022

Fixed with 9f3860e

@jcupitt jcupitt closed this as completed Jun 12, 2022
@lovell
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lovell commented Jun 13, 2022

@jcupitt It looks like a couple of stray #define DEBUG snuck into commit 9f3860e

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jcupitt commented Jun 13, 2022

Ooop, sorry!

@JinEnMok JinEnMok mentioned this issue Mar 7, 2024
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