diff --git a/kindlecomicconverter/comic2ebook.py b/kindlecomicconverter/comic2ebook.py
index 4a0ed6c..b5977f6 100755
--- a/kindlecomicconverter/comic2ebook.py
+++ b/kindlecomicconverter/comic2ebook.py
@@ -40,7 +40,7 @@ from subprocess import STDOUT, PIPE
 from psutil import virtual_memory, disk_usage
 from html import escape as hescape
 
-from .shared import available_archive_tools, md5Checksum, getImageFileName, walkSort, walkLevel, sanitizeTrace, subprocess_run
+from .shared import available_archive_tools, getImageFileName, walkSort, walkLevel, sanitizeTrace, subprocess_run
 from . import comic2panel
 from . import image
 from . import comicarchive
@@ -78,7 +78,6 @@ def main(argv=None):
 
 
 def buildHTML(path, imgfile, imgfilepath):
-    imgfilepath = md5Checksum(imgfilepath)
     filename = getImageFileName(imgfile)
     deviceres = options.profileData[1]
     if not options.noprocessing and "Rotated" in options.imgMetadata[imgfilepath]:
@@ -425,7 +424,6 @@ def buildOPF(dstdir, title, filelist, cover=None):
                   "</container>"])
     f.close()
 
-
 def buildEPUB(path, chapternames, tomenumber, ischunked):
     filelist = []
     chapterlist = []
@@ -506,6 +504,7 @@ def buildEPUB(path, chapternames, tomenumber, ischunked):
                       "display: none;\n",
                       "}\n"])
     f.close()
+    build_html_start = perf_counter()
     for dirpath, dirnames, filenames in os.walk(os.path.join(path, 'OEBPS', 'Images')):
         chapter = False
         dirnames, filenames = walkSort(dirnames, filenames)
@@ -515,10 +514,12 @@ def buildEPUB(path, chapternames, tomenumber, ischunked):
                                      'cover' + getImageFileName(afile)[1])
                 options.covers.append((image.Cover(os.path.join(dirpath, afile), cover, options,
                                                    tomenumber), options.uuid))
-            filelist.append(buildHTML(dirpath, afile, os.path.join(dirpath, afile)))
             if not chapter:
-                chapterlist.append((dirpath.replace('Images', 'Text'), filelist[-1][1]))
+                chapterlist.append((dirpath.replace('Images', 'Text'), afile))
                 chapter = True
+            filelist.append(buildHTML(dirpath, afile, os.path.join(dirpath, afile)))
+    build_html_end = perf_counter()
+    print(f"buildHTML: {build_html_end - build_html_start} seconds")
     # Overwrite chapternames if tree is flat and ComicInfo.xml has bookmarks
     if not chapternames and options.chapters and not ischunked:
         chapterlist = []
@@ -566,10 +567,13 @@ def imgDirectoryProcessing(path):
     if GUI:
         GUI.progressBarTick.emit(str(pagenumber))
     if len(work) > 0:
+        img_processing_start = perf_counter()
         for i in work:
             workerPool.apply_async(func=imgFileProcessing, args=(i,), callback=imgFileProcessingTick)
         workerPool.close()
         workerPool.join()
+        img_processing_end = perf_counter()
+        print(f"imgFileProcessing: {img_processing_end - img_processing_start} seconds")
         if GUI and not GUI.conversionAlive:
             rmtree(os.path.join(path, '..', '..'), True)
             raise UserWarning("Conversion interrupted.")
@@ -809,6 +813,7 @@ def sanitizeTree(filetree):
             key = os.path.join(root, name)
             if key != newKey:
                 os.replace(key, newKey)
+                options.imgMetadata[newKey] = options.imgMetadata.pop(key)
         for i, name in enumerate(dirs):
             tmpName = name
             slugified = slugify(name)
@@ -820,6 +825,10 @@ def sanitizeTree(filetree):
             if key != newKey:
                 os.replace(key, newKey)
                 dirs[i] = newKey
+                existingImgPathKeys = list(options.imgMetadata.keys())
+                for imgPath in existingImgPathKeys:
+                    if imgPath.startswith(key):
+                        options.imgMetadata[newKey + imgPath.removeprefix(key)] = options.imgMetadata.pop(imgPath)
     return chapterNames
 
 
diff --git a/kindlecomicconverter/image.py b/kindlecomicconverter/image.py
index 4398c89..4d6a655 100755
--- a/kindlecomicconverter/image.py
+++ b/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))
 
diff --git a/kindlecomicconverter/shared.py b/kindlecomicconverter/shared.py
index 76c579f..7a98d22 100644
--- a/kindlecomicconverter/shared.py
+++ b/kindlecomicconverter/shared.py
@@ -75,16 +75,6 @@ def walkLevel(some_dir, level=1):
             del dirs[:]
 
 
-def md5Checksum(fpath):
-    with open(fpath, 'rb') as fh:
-        m = md5()
-        while True:
-            data = fh.read(8192)
-            if not data:
-                break
-            m.update(data)
-        return m.hexdigest()
-
 
 def sanitizeTrace(traceback):
     return ''.join(format_tb(traceback))\