This is a copy of a chat between Claude AI and I a human. Files produced by Claude are in: https://www.rsok.com/~jrm/rggb2dng/debian/

WARNING: This is code written by an AI chatbot and I did not check for hallucinations. There are source and binary .deb files for experimenting on Debian. I make no promises for the work of Claude AI. Please read the source code before using.

RGGB TIFF to DNG raw file converter
Shared by John

This is a copy of a chat between Claude and John. Content may include unverified or unsafe content that do not represent the views of Anthropic. Shared snapshot may contain attachments and data not displayed here.

An example program that comes with the libraw source code will read a raw file and produce 4 tiff files, one for each of the RGGB colors.

Please write a command line program in C++ that will read four TIFF files representing RGGB and reassemble them into a DNG raw file than can be demosaiced using one of the algorithms in rawtherapee on Debian Trixie.

The program should check that the number of pixels in each of the four tiff files is compatible with such reassembly into a raw file.

The program should compile cleanly using Clang, clang-format, and clang-tidy.

There should be test code. Run time errors should be fixed and reported in release notes.

There should be scripts to create source and binary packages suitable for Debian Trixie. The result should be compatible with Debian Policy. A license similar to those for libraries that are packaged for Debian should be used.

Debian Trixie dependencies should be listed.

Rawtherapee should recognize the DNG created by the program as raw image data.

File contents should be determined in a manner similar to the POSIX standard program named "file" and not only guessed from the filename.

Cmake should be used.

deb files should be created that are similar to those in Debian unstable.

Apt or aptitude should be able too install the deb files on Trixie without conflicts with other Debian packages.

11:21 AM

Continue

11:32 AM

Continue

11:37 AM

Continue

11:43 AM

Continue

11:54 AM
bash
sudo apt install cmake clang clang-tidy clang-format libtiff-dev libmagic-dev pkg-config
cd rggb2dng-1.0.0
cmake -B build -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ \
      -DCMAKE_BUILD_TYPE=RelWithDebInfo
cmake --build build
ctest --test-dir build --output-on-failure
# Build .deb
dpkg-buildpackage -us -uc -b

I did download all. I did unzip of files.zip . I did "cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++" as the readme said to.

cmake --build build wrote many error messages.

2:21 PM

I get an error now with the new files. Did I make a mistake or did you make a mistake?

CMake Error: File /media/iMac_WD14TB/transfer/rggb2dng/cmake/version.hpp.in does not exist. CMake Error at CMakeLists.txt:68 (configure_file):   configure_file Problem configuring file

2:32 PM

That's my mistake. The cmake/version.hpp.in file is inside the tarball but you may only have extracted the individually-delivered files. Let me check what's needed and provide the fix.

You have two options:

Option A — simplest fix: Create the missing file manually. It's only 5 lines:

Create the file cmake/version.hpp.in (that directory and filename, relative to CMakeLists.txt) with this content:

cpp
#pragma once
// Auto-generated by CMake — do not edit
#define RGGB2DNG_VERSION "@PROJECT_VERSION@"
#define RGGB2DNG_VERSION_MAJOR @PROJECT_VERSION_MAJOR@
#define RGGB2DNG_VERSION_MINOR @PROJECT_VERSION_MINOR@
#define RGGB2DNG_VERSION_PATCH @PROJECT_VERSION_PATCH@
```

So on your system that would be:
```
/media/iMac_WD14TB/transfer/rggb2dng/cmake/version.hpp.in

Option B — remove the dependency entirely by patching CMakeLists.txt. The version string is only used in main.cpp for --version. Replace the configure_file block with a simple compile definition instead:

Edited 4 files, ran 3 commands, read a file

That was my mistake — the cmake/version.hpp.in file existed in the full source tree but wasn't included in the individually-delivered files, and CMakeLists.txt referenced it unconditionally.

The fix removes the generated header entirely. RGGB2DNG_VERSION is now passed as a single add_compile_definitions() call at the top of CMakeLists.txt, which is actually cleaner — no cmake/ subdirectory needed, no configure_file, and the version string is still derived from project(... VERSION 1.0.0) so it stays in sync automatically.

Replace your existing CMakeLists.txt with the one above (or extract it from the new tarball) and re-run:

bash
cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo \
      -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
cmake --build build

I got another error message: 

ctest --test-dir build --output-on-failure Internal ctest changing into directory: /media/iMac_WD14TB/transfer/rggb2dng/rggb2dng-1.0.0/build Test project /media/iMac_WD14TB/transfer/rggb2dng/rggb2dng-1.0.0/build     Start 1: unit_tests Process not started  /media/iMac_WD14TB/transfer/rggb2dng/rggb2dng-1.0.0/build/test_rggb2dng [permission denied] 1/1 Test #1: unit_tests .......................***Not Run   0.00 sec

0% tests passed, 1 tests failed out of 1

Total Test time (real) =   0.02 sec

The following tests FAILED:   1 - unit_tests (BAD_COMMAND) Errors while running CTest

2:38 PM

My mistake again. CMake built the test binary but didn't set the execute bit on it. This is a CMake property I forgot to set. Fix CMakeLists.txt:

Ran 3 commands, edited 2 files
+4-1
+4-1
Done

The error message [permission denied] on a path under /media/iMac_WD14TB is the real problem — that drive is almost certainly NTFS or exFAT, which doesn't support Unix execute permissions. Linux will not run binaries from such a volume directly.

The fix is to build in your home directory, not on the external drive. Replace your cmake invocation with:

bash
# Copy the source to your home directory first
cp -r /media/iMac_WD14TB/transfer/rggb2dng/rggb2dng-1.0.0 ~/rggb2dng
cd ~/rggb2dng

cmake -B build \
  -DCMAKE_BUILD_TYPE=RelWithDebInfo \
  -DCMAKE_C_COMPILER=clang \
  -DCMAKE_CXX_COMPILER=clang++

cmake --build build
ctest --test-dir build --output-on-failure

The source files themselves can live on NTFS (they're just text), but the build directory must be on a native Linux filesystem (ext4, btrfs, etc.) so that the compiled binaries get the execute bit set.

I've also updated CMakeLists.txt to use $<TARGET_FILE:test_rggb2dng> (the full absolute path to the binary) rather than just the target name, which is more robust regardless of filesystem:

Ran a command, read a file
Done

Summary: this one was not your mistake. The source code and CMakeLists are correct — the problem is that Linux cannot execute binaries compiled onto an NTFS/exFAT drive because those filesystems have no concept of Unix execute permissions, so every binary on them appears non-executable to the kernel.

The solution is simply:

bash
cp -r /media/iMac_WD14TB/transfer/rggb2dng/rggb2dng-1.0.0 ~/rggb2dng
cd ~/rggb2dng
cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo \
      -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
cmake --build build
ctest --test-dir build --output-on-failure

I seems like maybe there is another error

3:33 PM

Please paste the error message and I'll diagnose it.

make[1]: Leaving directory '/home/jrm/src/rggb2dng/rggb2dng-1.0.0/obj-x86_64-linux-gnu'    dh_install -O--buildsystem=cmake dh_install: warning: Cannot find (any matches for) "usr/bin/rggb2dng" (tried in ., debian/tmp)

dh_install: warning: rggb2dng missing files: usr/bin/rggb2dng dh_install: warning: Cannot find (any matches for) "usr/share/man/man1/rggb2dng.1*" (tried in ., debian/tmp)

dh_install: warning: rggb2dng missing files: usr/share/man/man1/rggb2dng.1* dh_install: error: missing files, aborting make: *** [debian/rules:6: binary] Error 255 dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2

3:33 PM

It seems that there might be another error: 

make[2]: Leaving directory '/home/jrm/src/rggb2dng/rggb2dng-1.0.0/obj-x86_64-linux-gnu' make[1]: Leaving directory '/home/jrm/src/rggb2dng/rggb2dng-1.0.0'    dh_install -O--buildsystem=cmake install -m0755 -d debian/rggb2dng//usr/bin cp --reflink=auto -a debian/tmp/usr/bin/rggb2dng debian/rggb2dng//usr/bin/ install -m0755 -d debian/rggb2dng//usr/share/doc/rggb2dng cp --reflink=auto -a debian/tmp/usr/share/doc/rggb2dng/CHANGES.md debian/tmp/usr/share/doc/rggb2dng/README.md debian/tmp/usr/share/doc/rggb2dng/copyright debian/rggb2dng//usr/share/doc/rggb2dng/ install -m0755 -d debian/rggb2dng//usr/share/man/man1 cp --reflink=auto -a debian/tmp/usr/share/man/man1/rggb2dng.1 debian/rggb2dng//usr/share/man/man1/    dh_installdocs -O--buildsystem=cmake install -p -m0644 debian/copyright debian/rggb2dng/usr/share/doc/rggb2dng/copyright    dh_installchangelogs -O--buildsystem=cmake install -m0755 -d debian/rggb2dng/usr/share/doc/rggb2dng install -p -m0644 debian/.debhelper/generated/rggb2dng/dh_installchangelogs.dch.trimmed debian/rggb2dng/usr/share/doc/rggb2dng/changelog.Debian mv debian/rggb2dng/usr/share/doc/rggb2dng/CHANGES.md debian/rggb2dng/usr/share/doc/rggb2dng/changelog chmod 0644 -- debian/rggb2dng/usr/share/doc/rggb2dng/changelog    dh_installman -O--buildsystem=cmake man-recode --to-code UTF-8 --suffix .dh-new debian/rggb2dng/usr/share/man/man1/rggb2dng.1 mv debian/rggb2dng/usr/share/man/man1/rggb2dng.1.dh-new debian/rggb2dng/usr/share/man/man1/rggb2dng.1 chmod 0644 -- debian/rggb2dng/usr/share/man/man1/rggb2dng.1    dh_installsystemduser -O--buildsystem=cmake    dh_perl -O--buildsystem=cmake    dh_link -O--buildsystem=cmake    dh_strip_nondeterminism -O--buildsystem=cmake    dh_compress -O--buildsystem=cmake cd debian/rggb2dng chmod a-x usr/share/doc/rggb2dng/changelog usr/share/doc/rggb2dng/changelog.Debian usr/share/man/man1/rggb2dng.1 gzip -9nf usr/share/doc/rggb2dng/changelog usr/share/doc/rggb2dng/changelog.Debian usr/share/man/man1/rggb2dng.1 cd '/home/jrm/src/rggb2dng/rggb2dng-1.0.0'    dh_fixperms -O--buildsystem=cmake find debian/rggb2dng ! -type l -a -true -a -true -print0 2>/dev/null | xargs -0r chmod go=rX,u+rw,a-s find debian/rggb2dng/usr/share/doc -type f -a -true -a ! -regex 'debian/rggb2dng/usr/share/doc/[^/]*/examples/.*' -print0 2>/dev/null | xargs -0r chmod 0644 find debian/rggb2dng/usr/share/doc -type d -a -true -a -true -print0 2>/dev/null | xargs -0r chmod 0755 find debian/rggb2dng/usr/share/man -type f -a -true -a -true -print0 2>/dev/null | xargs -0r chmod 0644 find debian/rggb2dng -type f \( -name '*.so.*' -o -name '*.so' -o -name '*.la' -o -name '*.a' -o -name '*.js' -o -name '*.css' -o -name '*.scss' -o -name '*.sass' -o -name '*.jpeg' -o -name '*.jpg' -o -name '*.png' -o -name '*.gif' -o -name '*.cmxs' -o -name '*.node' \) -a -true -a -true -print0 2>/dev/null | xargs -0r chmod 0644 find debian/rggb2dng/usr/bin -type f -a -true -a -true -print0 2>/dev/null | xargs -0r chmod a+x    dh_missing -O--buildsystem=cmake    dh_dwz -a -O--buildsystem=cmake dwz -- debian/rggb2dng/usr/bin/rggb2dng dwz: debian/rggb2dng/usr/bin/rggb2dng: Unknown debugging section .debug_addr dh_dwz: error: dwz -- debian/rggb2dng/usr/bin/rggb2dng returned exit code 1 dh_dwz: error: Aborting due to earlier error make: *** [debian/rules:7: binary] Error 2 dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2

3:38 PM

My mistake. dwz is trying to optimise DWARF debug info but fails on the debug sections produced by Clang. Fix debian/rules to disable dh_dwz:

Ran 2 commands, read a file
Done

Replace debian/rules with debian_rules (rename it after downloading) and run dpkg-buildpackage -us -uc -b again.

The fix is a single empty override_dh_dwz: target in debian/rules. When debhelper sees an override with no body it skips that step entirely. dwz is a DWARF compressor that works well with GCC's debug output but chokes on Clang's .debug_addr sections (introduced in DWARF v5, which Clang emits by default). Since dwz only saves disk space on the debug symbols and isn't required for a working package, skipping it is the correct Debian approach for Clang-built packages.

I see only a binary deb and no source deb: 

find . -iname "*.deb" -ls  80095603     28 -rw-r--r--   1 jrm      jrm         26700 Mar 20 15:39 ./rggb2dng_1.0.0-1_amd64.deb  80095604    120 -rw-r--r--   1 jrm      jrm        118936 Mar 20 15:39 ./rggb2dng-dbgsym_1.0.0-1_amd64.deb

3:42 PM

That's expected — dpkg-buildpackage -us -uc -b only builds binary packages (the -b flag means binary-only). To get a source package as well you need to drop the -b flag, but that also requires an orig tarball in the parent directory. Here is the correct procedure:

bash
cd ~/src/rggb2dng

# Put the orig tarball one level up (where dpkg-buildpackage expects it)
cp rggb2dng_1.0.0.orig.tar.xz ../ 2>/dev/null || true

# Build both source and binary packages, unsigned
cd rggb2dng-1.0.0
dpkg-buildpackage -us -uc
```

That will produce in `~/src/rggb2dng/`:
```
rggb2dng_1.0.0-1.dsc
rggb2dng_1.0.0.orig.tar.xz
rggb2dng_1.0.0-1.debian.tar.xz
rggb2dng_1.0.0-1_amd64.deb
rggb2dng-dbgsym_1.0.0-1_amd64.deb
rggb2dng_1.0.0-1_amd64.buildinfo
rggb2dng_1.0.0-1_amd64.changes

The .dsc plus the two tarballs together form the source package. If you want to verify it is a valid source package:

bash
cd ~/src/rggb2dng
dpkg-source --info rggb2dng_1.0.0-1.dsc

And to confirm the binary installs cleanly:

bash
sudo apt install ./rggb2dng_1.0.0-1_amd64.deb
rggb2dng --version

The rggb2dng-dbgsym package you already have is normal — debhelper automatically splits debug symbols into a separate -dbgsym package, which is correct Debian practice.

What mistake did I make this time:

3:48 PM

This one is your mistake, but an easy one to make. You ran cmake --build build (or built into a build/ directory) inside the source tree before running dpkg-buildpackage. The 3.0 (quilt) source format cannot include binary files in the diff against the orig tarball, and your build/ directory full of compiled objects is now sitting inside the source tree.

Fix it by cleaning out the build directory first:

bash
cd ~/src/rggb2dng/rggb2dng-1.0.0
rm -rf build/
dpkg-buildpackage -us -uc

Debhelper builds into obj-x86_64-linux-gnu/ (not build/) and cleans that up automatically between runs. Your manual cmake -B build earlier left behind a build/ directory that dpkg-source then tried to include in the source package.

In future, if you want to do a manual test build before packaging, either use the debhelper build directory name:

bash
cmake -B obj-x86_64-linux-gnu ...

or build completely outside the source tree:

bash
cmake -B /tmp/rggb2dng-build -S ~/src/rggb2dng/rggb2dng-1.0.0 ...

That way dpkg-buildpackage never sees the compiled artefacts.

Thanks for the lesson. It seems to work now. Do I need to share the chat again to share all of the bug fixes, both yours and mine?

3:54 PM

No, you don't need to share the chat again. Everything is already captured in the source package you just built successfully. The authoritative record of all the fixes is:

  • CHANGES.md inside the package documents all five runtime bugs that were found and fixed during development
  • debian/changelog records the package version and release
  • The source package (.dsc + orig tarball + debian tarball) contains the final corrected state of all files

If you want to share the package with others, just give them the three source package files from ~/src/rggb2dng/:

rggb2dng_1.0.0-1.dsc
rggb2dng_1.0.0.orig.tar.xz
rggb2dng_1.0.0-1.debian.tar.xz

Anyone on Debian Trixie can then install from the binary deb directly, or reconstruct the source with:

bash
dpkg-source -x rggb2dng_1.0.0-1.dsc

The one thing worth noting if you do want to share this more widely: debian/changelog and debian/control still have the placeholder Maintainer <maintainer@example.com> — you would want to replace that with your real name and email address before distributing or uploading anywhere official.

I wish to share our complete dialog as I learned how to make this program. I got a public link to this Claude chat, but it does not seem to show the part of the dialog after I shared the link

3:55 PM

That's a Claude.ai limitation — a shared chat link only captures the conversation up to the moment the link was generated. Any messages after that point are not included.

To share the complete dialog including all the bug fixes, you have a few options:

Easiest — generate a new share link now. Go to the share button again and create a fresh link. It will capture everything up to this moment.

Export to a file. Most browsers let you save a page as HTML or PDF. With the chat fully scrolled, use your browser's print function (Ctrl+P or Cmd+P) and choose "Save as PDF". That captures everything visible on screen regardless of when the link was shared.

Copy and paste. Select all the text in the chat window and paste it into a document. This works but loses formatting.

The new share link approach is simplest — just delete or ignore the old link and share the new one. Everything in this conversation, including all the build errors and fixes, will be visible to anyone who opens it.

Start your own conversation