Godot crashes when importing 1x1 pixel JPEG image using YCbCr and 2x2 sampling factor

[EdThePro101]

Godot version:
Godot 3.2.3

OS/device including version:

• Device: Acer Aspire A315-33
• OS: Windows 10 64-bit
• CPU: Intel(R) Celeron(R) N3060 @ 1.60 GHz
• GPU: Intel HD Graphics 400
• RAM: 4GB

Issue description:
I was following an answer on the Godot forum about making a coloured rectangle, and using Microsoft Paint, I made a white 1x1 pixel JPEG image and placed it in my project's .\Images\ directory. When I opened Godot to rescan for assets, Godot crashed as it was importing .\Images\Background.jpg.

Steps to reproduce:

1. Create an empty Godot project.
2. In the small File Explorer view on the bottom left, right-click on res:// and create a folder called Scenes.
3. Open MS Paint.
4. Go to File -> Preferences .
5. Change both width and height to 1 pixel.
6. Tap on the white colour in the colour palette.
7. Tap on the single pixel (may need to zoom in).
8. Go to File -> Save As... -> JPEG image.
9. Go to the project's directory and make a new folder called Images.
10. Save the JPEG image as Background.jpeg or Background.jpg.
11. Open Godot and let Godot scan the project's assets.
12. The crash occurs when scanning Background.jpeg.

Minimal reproduction project:
I've added the original project.

ForEx Simulator.zip

[Calinou]

I can't reproduce this on Godot 3.2.3 with JPEGs generated by ImageMagick (convert -size 1x1 xc:"#fff" 1x1.jpg). However, I can reproduce this with your MRP:

godot.x11.tools.64.llvm: thirdparty/jpeg-compressor/jpgd.h:278: int jpgd::jpeg_decoder::check_sample_buf_ofs(int) const: Assertion `ofs >= 0' failed.

My minimal reproduction project: small_jpeg_import_crash.zip

file information for your MRP:

Background.jpg: JPEG image data, JFIF standard 1.01, resolution (DPI), density 96x96, segment length 16, baseline, precision 8, 1x1, components 3

file information for my MRP:

1x1.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 1x1, components 1
1x2.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 1x2, components 1
2x2.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 2x2, components 1
2x3.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 2x3, components 1
2x4.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 2x4, components 1
4x4.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 4x4, components 1

[timothyqiu]

I can reproduce this with JPEGs generated by ImageMagick if I set the colorspace to YCbCr and use a sampling factor of 2x2:

convert -size 1x1 xc:"#fff" -sampling-factor 2x2 -colorspace ycbcr 1x1.jpg

This produces the same backtrace as the MRP.

[alketii]

This is happening to me also, while trying to import a .dae file with a 1x2 texture.

[Bhu1-V]

hello,
I want To work on this i understood the problem but i really don't known where to start .
I imported the MRP saw that it got froze at Importing assets dialog and Crashed, so I think i should start by checking code for importing project and importing assets functions but, it's hard to find.

Any help regarding this Is Appreciated.

[akien-mga]

If you can reproduce the crash, use a debugger to get a stacktrace, which will show you which files are involved.

There's a hint in #42363 (comment):

godot.x11.tools.64.llvm: thirdparty/jpeg-compressor/jpgd.h:278: int jpgd::jpeg_decoder::check_sample_buf_ofs(int) const: Assertion `ofs >= 0' failed.

You can then search which files include this file:

$ rg "jpgd.h"
thirdparty/jpeg-compressor/jpgd.cpp
29:#include "jpgd.h"

thirdparty/jpeg-compressor/jpgd.h
1:// jpgd.h - C++ class for JPEG decompression.

modules/jpg/image_loader_jpegd.cpp
36:#include <jpgd.h>

(But again a stacktrace would show you that the crash in thirdparty/jpeg-compressor/jpgd.h originates in modules/jpg/image_loader_jpegd.cpp, and would additionally give you the relevant line and further call stack for what triggers that image loader call in the editor import code.)

[Bhu1-V]

So, I checked the code int b = (c_x1 >> 3) * BLOCKS_PER_MCU * 64 + (c_x1 & 7); which is in file thirdparty/jpeg-compressor/jpgd.cpp on Line 2061

above value b becoming negative which eventually on the next line :
int cb10_sample = p_C0Samples[check_sample_buf_ofs(b + y0_base)];
is used to call check_sample_buf_ofs() which checks whether passed argument is positive or not
(check check_sample_buf_ofs() defination ) and closes the program when it's negative -> CAUSE OF ERROR

Then, I tried to read the function in which this whole thing is implemented and found out that it is uint32_t jpeg_decoder::H2V2ConvertFiltered() Fuction.

now i am really stuck on what to do next because i don't see anything wrong in the implementation.

If i am missing something. I'm Happy to learn it.