huge speed optimization on HDD by removing md5 (#845)

* Eliminate unnecessary use of MD5 checksum

md5checksum() computes the actual checksum of a specified file, which is appropriately expensive, but the code seemed to be using the checksum result as a key into the imgMetadata dictionary to avoid handling image files being renamed during processing steps. This seems like a very expensive way to handle the rename so instead, I now update the imgMetadata keys with the new filename in the one place that the rename happens, and avoid MD5 checksums entirely.

* merge conflicts

* Add missing handling for image path renames due to nested chapter folder name

* merge conflicts

* merge conflicts

* add perf_counters

* imgFileProcessing perf_counter

* use startswith and removeprefix

---------

Co-authored-by: utopiafallen <utopiafallen@gmail.com>

kindlecomicconverter/image.py

@@ -22,7 +22,6 @@ import io
 import os
 import mozjpeg_lossless_optimization
 from PIL import Image, ImageOps, ImageStat, ImageChops, ImageFilter
-from .shared import md5Checksum
 from .page_number_crop_alg import get_bbox_crop_margin_page_number, get_bbox_crop_margin
 from .inter_panel_crop_alg import crop_empty_inter_panel
 
@@ -321,7 +320,7 @@ class ComicPage:
                             output_jpeg_file.write(output_jpeg_bytes)
                 else:
                     self.image.save(self.targetPath, 'JPEG', optimize=1, quality=85)
-            return [md5Checksum(self.targetPath), flags, self.orgPath]
+            return [self.targetPath, flags, self.orgPath]
         except IOError as err:
             raise RuntimeError('Cannot save image. ' + str(err))