Support reading from stdin, writing to stdout in HEIC2PNG

src/heic2png/__init__.py

@@ -1,4 +1,4 @@
 __version__ = "1.1.4"
 
-from .heic2png import *
-from .cli import main
+#from .heic2png import *
+#from .cli import main

src/heic2png/cli.py

@@ -1,71 +1,83 @@
+import sys
 import traceback
 import argparse
 from pillow_heif import register_heif_opener
 
-from . import __version__
-from .heic2png import HEIC2PNG
+from heic2png import __version__
+from heic2png.heic2png import HEIC2PNG
+
+
+def eprint(*args, file=sys.stderr, **kwds):
+    "print to stderr by default"
+    print(*args, file=file, **kwds)
 
 def cli(args):
     """
     Command Line Interface for converting HEIC images to PNG.
 
     :param args: Parsed command-line arguments.
     """
-    print(f'Processing the HEIC image at `{args.input_path}`')
+    eprint(f'Processing the HEIC image at `{args.input_path}`')
 
     if args.output_path:
-        print(f'Specified output path: `{args.output_path}`')
+        eprint(f'Specified output path: `{args.output_path}`')
 
     if args.quality and not 1 <= args.quality <= 100:
-        print('Error: Quality should be a value between 1 and 100.')
+        eprint('Error: Quality should be a value between 1 and 100.')
         return
 
     try:
-        print('==========================')
-        print('==== HEIC2PNG Options ====')
-        print('==========================')
-        print(f'>> Input file path: {args.input_path}')
-        print(f'>> Output file path: {args.output_path}')
-        print(f'>> Quality: {args.quality}')
-        print(f'>> Overwrite: {args.overwrite}')
-        print('==========================')
+        eprint('==========================')
+        eprint('==== HEIC2PNG Options ====')
+        eprint('==========================')
+        eprint(f'>> Input file path: {args.input_path}')
+        eprint(f'>> Output file path: {args.output_path}')
+        eprint(f'>> Quality: {args.quality}')
+        eprint(f'>> Overwrite: {args.overwrite}')
+        eprint('==========================')
         heic_img = HEIC2PNG(args.input_path, args.quality, args.overwrite)
-        print('Converting the image...')
+        eprint('Converting the image...')
 
         if args.output_path and args.overwrite:
-            print(f'Overwriting the existing file at `{args.output_path}`')
+            eprint(f'Overwriting the existing file at `{args.output_path}`')
 
         output_path = heic_img.save(args.output_path)
-        print(f'Success! The converted image is saved at `{output_path}`')
+        eprint(f'Success! The converted image is saved at `{output_path}`')
 
     except FileExistsError:
-        print('Error: The specified output file already exists.')
-        print('Use the -w option to overwrite the existing file.')
+        eprint('Error: The specified output file already exists.')
+        eprint('Use the -w option to overwrite the existing file.')
 
     except ValueError as e:
-        print('Error: Invalid input or output format.')
-        print(e)
+        eprint('Error: Invalid input or output format.')
+        eprint(e)
         traceback.print_exc()
 
     except Exception as e:
-        print(f'An unexpected error occurred: {e}')
-        print('Here are the details:')
-        print('==========================')
+        eprint(f'An unexpected error occurred: {e}')
+        eprint('Here are the details:')
+        eprint('==========================')
         traceback.print_exc()
-        print('==========================')
-        print('Please report this issue with the full traceback.')
-        print('-> https://github.com/NatLee/HEIC2PNG/issues')
+        eprint('==========================')
+        eprint('Please report this issue with the full traceback.')
+        eprint('-> https://github.com/NatLee/HEIC2PNG/issues')
+
+
 
 def main():
     """
     Main function to register the HEIF opener and initiate the argparse CLI.
     """
     register_heif_opener()
 
-    print(f'HEIC2PNG v{__version__}')
+    eprint(f'HEIC2PNG v{__version__}')
 
-    parser = argparse.ArgumentParser(description="Convert HEIC images to PNG.")
-    parser.add_argument("-i", "--input_path", required=True, help="Path to the input HEIC image.")
+    parser = argparse.ArgumentParser(description="Convert HEIC images to PNG.",
+        epilog="""
+In the absence of an input (-i) file, input is read from sys.stdin.
+In the absence of an output (-o) file, output is written to sys.stdout.
+""")
+    parser.add_argument("-i", "--input_path", help="Path to the input HEIC image.")
     parser.add_argument("-o", "--output_path", help="Path to save the converted PNG image.")
     parser.add_argument("-q", "--quality", type=int, help="Quality of the converted PNG image (1-100).")
     parser.add_argument("-w", "--overwrite", action="store_true", help="Overwrite the existing file if it already exists.")

src/heic2png/heic2png.py

@@ -1,52 +1,67 @@
+import os
+import sys
 import subprocess
 from pathlib import Path
 from typing import Optional
+
 from PIL import Image
 from pillow_heif import register_heif_opener
 
 register_heif_opener()
 
 class HEIC2PNG:
-    def __init__(self, image_file_path: str, quality: Optional[int] = None, overwrite: bool = False):
+    def __init__(self, image_file_path: Optional[str] = "",
+                 quality: Optional[int] = None,
+                 overwrite: bool = False):
         """
         Initializes the HEIC2PNG converter.
 
         :param image_file_path: Path to the HEIC image file.
         :param quality: Quality of the converted PNG image (1-100).
         :param overwrite: Whether to overwrite the file if it already exists.
         """
-        self.image_file_path: Path = Path(image_file_path)
+        if not image_file_path:
+            stdin = (os.fdopen(sys.stdin.fileno(), "rb")
+                if "b" not in sys.stdin.mode else sys.stdin)
+            self.image_file_path = stdin
+        # TODO: I'm not a Python type hints maven. The image_file_path type
+        # needs to reflect that an open file object is also acceptable.
+        elif hasattr("fileno", image_file_path):
+            pass                        # already open file
+        else:
+            self.image_file_path: Path = Path(image_file_path)
+            if self.image_file_path.suffix.lower() != '.heic':
+                raise ValueError("The provided file is not a HEIC image.")
         self.quality: Optional[int] = quality
         self.overwrite: bool = overwrite
 
-        if not self.image_file_path.is_file():
-            raise FileNotFoundError(f"The file {image_file_path} does not exist.")
-
-        if self.image_file_path.suffix.lower() != '.heic':
-            raise ValueError("The provided file is not a HEIC image.")
-
         self.image: Image.Image = Image.open(self.image_file_path)
 
-    def save(self, output_image_file_path: Optional[str] = None, extension: str = '.png') -> Path:
+    def save(self, output_image_file_path: Optional[str] = "",
+             extension: str = '.png') -> Path:
         """
-        Converts and saves the HEIC image to PNG format.
+        Converts and saves the input image to another format.
+
+        The default output format is PNG.
 
         :param output_image_file_path: Path to save the converted PNG image.
         :param extension: The file extension of the converted image.
         :return: Path where the converted image is saved.
         """
-        if output_image_file_path:
-            output_path: Path = Path(output_image_file_path)
-            if output_path.suffix.lower() != extension:
-                raise ValueError("The output file extension does not match the specified extension.")
+        if not output_image_file_path:
+            stdout = (os.fdopen(sys.stdout.fileno(), "wb")
+                if "b" not in sys.stdout.mode else sys.stdout)
+            output_path = stdout
         else:
-            output_path: Path = self.image_file_path.with_suffix(extension)
-
-        if not self.overwrite and output_path.exists():
-            raise FileExistsError(f"The file {output_path} already exists.")
+            output_path: Path = Path(output_image_file_path)
 
-        self.image.save(output_path)
+        # TODO: Not sure this is correct, there's probably a better mapping
+        # between image file extensions and file formats. For example, see the
+        # output of `python -m PIL`.
+        self.image.save(output_path, format=extension.replace(".", "").upper())
 
+        # TODO: Skip this step if the output format isn't PNG or pngquant can't
+        # be found?
         # Optimize PNG with pngquant if quality is specified
         if self.quality and self.quality != 100:
             quality_str: str = f'{self.quality}-{self.quality}'

tests/test_heic2png.py

@@ -1,9 +1,13 @@
-import pytest
-import numpy as np
+import os
+import sys
 import subprocess
 from pathlib import Path
+
+import pytest
+import numpy as np
 from PIL import Image
 from pillow_heif import register_heif_opener
+
 from heic2png.heic2png import HEIC2PNG
 
 # Paths for test files
@@ -46,3 +50,21 @@ def test_quality(cleanup):
     high_quality_size = Path(TEST_HIGH_QUALITY_OUTPUT_FILENAME).stat().st_size
 
     assert low_quality_size < high_quality_size, "High quality image should be larger in size"
+
+def test_stdin_stdout():
+    inputfile = "tests/calder-flamingo.heic"
+    outputfile = "tests/calder-flamingo.png"
+    try:
+        save_stdin, save_stdout = (sys.stdin, sys.stdout)
+        if os.path.exists(outputfile):
+            os.unlink(outputfile)
+        with (open(inputfile, "rb") as sys.stdin,
+              open(outputfile, "wb") as sys.stdout):
+            converter = HEIC2PNG()
+            converter.save()
+    finally:
+        sys.stdin, sys.stdout = save_stdin, save_stdout
+        with (open(inputfile, "rb") as inp,
+              open(outputfile, "rb") as outp):
+            assert len(outp.read()) > len(inp.read())
+        os.unlink(outputfile)

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{37,38,39}
+envlist = py{37,38,39,310,311,312,313}
 minversion = 3.3.0
 isolated_build = true