Remove Dockerfile dependencies replaced by PyMuPDF

PyMuPDF replaced the need for almost all dependencies, which this commit
now removes.

We are also removing tesseract-ocr as a dependency since
(to our surprise) PyMuPDF ships directly with tesseract binaries [1].
However, now that tesseract-ocr is not available directly as a binary
tool, the `test_ocr.py` needed to be changed.

Fixes #658

[1]: https://github.com/freedomofpress/dangerzone/issues/658#issuecomment-1861033149

CHANGELOG.md

@@ -13,6 +13,7 @@ since 0.4.1, and this project adheres to [Semantic Versioning](https://semver.or
 ### Changed
 
 - Feature: Add support for HWP/HWPX files (Hancom Office) for macOS Apple Silicon devices ([issue #498](https://github.com/freedomofpress/dangerzone/issues/498), thanks to [@OctopusET](https://github.com/OctopusET))
+- Replace Dangerzone document rendering engine from pdftoppm PyMuPDF, essentially replacing a variety of tools (gm / tesseract / pdfunite / ps2pdf) ([issue #658](https://github.com/freedomofpress/dangerzone/issues/658))
 
 ## Dangerzone 0.5.1
 

Dockerfile

@@ -55,14 +55,10 @@ FROM alpine:latest
 # Install dependencies
 RUN apk --no-cache -U upgrade && \
     apk --no-cache add \
-    ghostscript \
     libreoffice \
     openjdk8 \
-    poppler-utils \
-    poppler-data \
     python3 \
     py3-magic \
-    tesseract-ocr \
     font-noto-cjk
 
 COPY --from=pymupdf-build /usr/lib/python3.11/site-packages/fitz/ /usr/lib/python3.11/site-packages/fitz

tests/test_ocr.py

@@ -1,5 +1,6 @@
 import platform
 import subprocess
+from pathlib import Path
 
 import pytest
 
@@ -16,16 +17,30 @@ def test_ocr_ommisions() -> None:
     # Create the command that will list all the installed languages in the container
     # image.
     runtime = Container.get_runtime()
-    command = [runtime, "run", Container.CONTAINER_NAME, "tesseract", "--list-langs"]
+    command = [
+        runtime,
+        "run",
+        Container.CONTAINER_NAME,
+        "find",
+        "/usr/share/tessdata/",
+        "-name",
+        "*.traineddata",
+    ]
 
     # Run the command, strip any extra whitespace, and remove the following first line
     # from the result:
     #
     #     List of available languages in "/usr/share/tessdata/" ...
-    installed_langs = set(
+    installed_langs_filenames = (
         subprocess.run(command, text=True, check=True, stdout=subprocess.PIPE)
         .stdout.strip()
-        .split("\n")[1:]
+        .split("\n")
+    )
+    installed_langs = set(
+        [
+            Path(filename).name.split(".traineddata")[0]
+            for filename in installed_langs_filenames
+        ]
     )
 
     # Remove the "osd" and "equ" languages from the list of installed languages, since