Add JPEG‑XL Support to libcupsfilters (WoC 4.0 Contribution) #82

TitikshaBansal · 2025-03-04T17:38:06Z

Add JPEG‑XL Support to libcupsfilters

This pull request adds initial support for the JPEG‑XL image format to libcupsfilters. With these changes, cups‑filters can now detect, decode, and convert JPEG‑XL files into PDF and raster formats, thereby enabling printing via CUPS.

Note: This pull request does not include modifications for MIME type definitions; those changes will be submitted in a separate pull request.

Overview

JPEG‑XL Detection

Function Updated: is_jpegxl() in image-jpeg-xl.c. Checks for both standard JPEG‑XL signature (\x00\x00\x00\x0C\x4A\x58\x4C\x20) and the JPEG‑XL stream signature (\xFF\x0A).

Decoding Implementation

New Functions:
- _cfImageReadJPEGXL()
- _cfImageOpenJPEGXL()
Core Decoder Function:
- cf_image_create_from_jxl_decoder()
  - Sets up a JxlPixelFormat requesting 16‑bit per channel output.
  - Processes the decoder input until the full image is decoded.
  - Detailed logging has been added via fprintf(stderr, ...) to log file size, status codes, and key variable values for debugging.

Build System Updates

Linking: The build configuration now uses pkg-config to link against libjxl.
Integration: The JPEG‑XL code integrates with existing filters for PDF and raster conversion.

Testing and Verification

Decoder Verification: The JPEG‑XL support was verified using the djxl tool and by testing conversions through cups‑filters.
Output Validation: Output PDF and raster files were inspected using utilities like rasterview to ensure correct color depth and page dimensions.
Debug Logging: Added extensive logging in the JPEG‑XL functions to assist in diagnosing any issues.

Future Work

Error Handling: Enhance error handling and add more comprehensive unit tests.
Optimizations: Further optimize performance and extend support for additional JPEG‑XL profiles.
MIME Type Integration: Develop and submit a separate PR for updating MIME type definitions for JPEG‑XL.

Background

This contribution was developed as part of the WoC 4.0 event organized by IIIT Kalyani. I have enjoyed working on integrating JPEG‑XL support into cups‑filters and am eager to continue contributing to this project even after the event concludes.

GitHub Repository: https://github.com/TitikshaBansal/libcupsfilters
Branch: features/jpegxl-support

Thank you for reviewing my contribution. I look forward to your feedback and further improvements.

Best regards,
Titiksha Bansal

Added an inclusion of your new header for JPEG‑XL support.

In the block that checks the header for PNG, JPEG, and TIFF, added a new branch for JPEG‑XL. We add an #ifdef HAVE_LIBJXL branch that calls _cfImageReadJPEGXL() if is_jpegxl() returns true. Now, whether the user is converting to PDF (via imagetopdf.c) or to Raster (via imagetoraster.c), they call cfImageOpen() (and thus cfImageOpenFP()) which now supports JPEG‑XL.

Created a header file for your JPEG‑XL functions.

Implemented the JPEG‑XL–specific functions. In this the extra parameters (primary, secondary, saturation, hue, lut) are passed but not used because the JPEG‑XL decoder (via libjxl) handles the uncompression and preserves full quality.

Implementation for cfImageCreateFromJxlDecoder(). This function uses the libjxl API to extract the frame header, compute the required output buffer size (requesting 16‑bit output for full quality), allocate memory for the decoded pixels, and then fill in a cf_image_t structure with the image properties.

Reverted the changes made earlier in the file.

Reverted all the changes made earlier.

Updated file to handle the errors encountered while make.

Made changes to handle errors during make

Updated file to handle errors encountered while make

cupsfilters/image.c

tillkamppeter · 2025-03-04T21:48:47Z

cupsfilters/image-jpeg-xl.c


-  // Process input until full image is decoded.
+  /* Process input until full image is decoded. */


For comments please use // ... and not /* ... */ to align with the other files of libcupsfilters (and with OpenPrinting's code style).

tillkamppeter · 2025-03-04T21:54:53Z

Please check the file DEVELOPING.md for information about coding style. Especially do the naming of functions as follows:

### Functions

Functions with a global scope have a lowercase prefix followed by capitalized
words, e.g., `cfDoThis`, `cfDoThat`, `cfDoSomethingElse`, etc.  Private
global functions begin with a leading underscore, e.g., `_cfDoThis`,
`_cfDoThat`, etc.

Functions with a local scope are declared static with lowercase names and
underscores between words, e.g., `do_this`, `do_that`, `do_something_else`, etc.

In short:

Public API of libcupsfilters: cfDoThis()
libcupsfilters-internal function used in more than one file: _cfDoThat()
static function (only used in the same file): do_something_else()

Makefile.am

cupsfilters/image-jpeg-xl.c

tillkamppeter · 2025-03-04T22:19:22Z

What is now missing is:

Please check each function whether
- it is used only in the file where it is defined/implemented: In this case declare it static and give to it an underscore-separated lowercase name. Do not declare such functions in any of the *.h files.
- it is used only inside libcupsfilters but also in other files than the one where it got defined/implemented: Do not declare it static, name it in camelCase, starting with _cf, and declare it in a private *.h file (image-*.h, *-private.h).
- Your work should not contain any new function for the public API, so do not name any of your functions in camelCase starting with cf.
Please make sure not to change the whitespace in any file which existed before your PR.

Please always test-build after each code change!!

updated the function names for the jpeg-xl support

fixed some debug errors.

Changed comment styling to align with OpenPrinting's code style.

tillkamppeter · 2025-03-05T12:31:28Z

cupsfilters/image.c

@@ -71,7 +78,7 @@ cfImageClose(cf_image_t *img)		// I - Image to close
    close(img->cachefile);
    unlink(img->cachename);
  }
-
+	


Please make sure not having any whitespace-only changes.

tillkamppeter · 2025-03-05T12:37:06Z

Thank you very much!

Function naming and comments are correct now.
image.c still contains many whitespace-only changes. Especially take care not adding whitespace at the end of a line.
Please add copyright/license/contents header comments to the files you have added, as other files, like image-jpeg.c have.
Check you CI testing, especially which packages get installed for the CI testing. Yesterday I have seen that the CI test had failed as the code did not build due to lack of libjxl.

Modified code to ensure that libjxl library is installed for CI testing.

Added header, copyrights and contents comments in the file

Added necessary comments in the file

Modified the copyright comments.

TitikshaBansal added 30 commits February 17, 2025 00:34

Update configure.ac for the input support

17427de

Update imagetopdf.c

6f94361

Updated imagetoraster.c for jpegxl input support

ab9c8e5

added jxl decoder

1976507

Update imagetoraster.c

f51bea4

Update imagetopdf.c

8a6147b

Updated image-private.h

a1c94c5

Added an inclusion of your new header for JPEG‑XL support.

Create image-jpeg-xl.h

34ee8de

Created a header file for your JPEG‑XL functions.

Create image-jpeg-xl.c

e540afb

Implemented the JPEG‑XL–specific functions. In this the extra parameters (primary, secondary, saturation, hue, lut) are passed but not used because the JPEG‑XL decoder (via libjxl) handles the uncompression and preserves full quality.

Update imagetopdf.c

f88fb14

Reverted the changes made earlier in the file.

Update imagetoraster.c

d950436

Reverted all the changes made earlier.

Update image-jpeg-xl.h

a642841

Update image-jpeg-xl.c

848a6d0

Update Makefile.am

55694dd

Update image-jpeg-xl.h

9ee3a7e

Updated file to handle the errors encountered while make.

Update image-jpeg-xl.c

f695114

Made changes to handle errors during make

Update image.c

f83a11a

Updated file to handle errors encountered while make

Update image.c

a32702b

Update Makefile.am

9ef007d

Update image-jpeg-xl.c

0482e95

Update image-jpeg-xl.c

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Update image.c

a5abe34

Update image-jpeg-xl.c

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Update image.c

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Update image-jpeg-xl.c

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Update image-jpeg-xl.c

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Update Makefile.am

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Update Makefile.am

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TitikshaBansal added 5 commits March 5, 2025 01:33

Update image-jpeg-xl.c

1a811f5

Update image-jpeg-xl.c

13976a9

Update image-jpeg-xl.c

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Update image.c

fbb24da

Update image-jpeg-xl.c

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tillkamppeter reviewed Mar 4, 2025

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TitikshaBansal added 10 commits March 5, 2025 14:49

Update image.c

b372d5c

Update Makefile.am

b201466

Update image.c

81b8caa

updated the function names for the jpeg-xl support

Update image-jpeg-xl.c

d1f6d56

Update image-jpeg-xl.c

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Update image-jpeg-xl.c

935623d

fixed some debug errors.

Update image-jpeg-xl.h

f7528f4

Update image-jpeg-xl.c

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3320a71

Update image-jpeg-xl.c

c631730

Changed comment styling to align with OpenPrinting's code style.

tillkamppeter reviewed Mar 5, 2025

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TitikshaBansal added 6 commits March 5, 2025 20:32

Update build.yaml to support .jxl files.

8cf1bf4

Modified code to ensure that libjxl library is installed for CI testing.

Update image-jpeg-xl.c

fc24819

Added header, copyrights and contents comments in the file

Update image-jpeg-xl.h

8ab496f

Added necessary comments in the file

Update image.c

a2c1646

Update image-jpeg-xl.c

a26b659

Update image-jpeg-xl.h

cc00492

Modified the copyright comments.

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Add JPEG‑XL Support to libcupsfilters (WoC 4.0 Contribution) #82

Add JPEG‑XL Support to libcupsfilters (WoC 4.0 Contribution) #82

TitikshaBansal commented Mar 4, 2025

tillkamppeter Mar 4, 2025

tillkamppeter commented Mar 4, 2025

tillkamppeter commented Mar 4, 2025

tillkamppeter Mar 5, 2025

tillkamppeter commented Mar 5, 2025


		// Process input until full image is decoded.
		/* Process input until full image is decoded. */

Add JPEG‑XL Support to libcupsfilters (WoC 4.0 Contribution) #82

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Add JPEG‑XL Support to libcupsfilters (WoC 4.0 Contribution) #82

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TitikshaBansal commented Mar 4, 2025

Add JPEG‑XL Support to libcupsfilters

Overview

JPEG‑XL Detection

Decoding Implementation

Build System Updates

Testing and Verification

Future Work

Background

tillkamppeter Mar 4, 2025

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tillkamppeter commented Mar 5, 2025