add webp output support (ignored for Kindle MOBI/EPUB and all PDF) (#1290)

* add webp output support (ignored for Kindle MOBI/EPUB)

* disable png extra optons by default

* pdf webp is not supported

kindlecomicconverter/comic2ebook.py

@@ -353,6 +353,8 @@ def buildOPF(dstdir, title, filelist, originalpath, cover=None):
             mt = 'image/png'
         elif '.gif' == filename[1]:
             mt = 'image/gif'
+        elif '.webp' == filename[1]:
+            mt = 'image/webp'
         else:
             mt = 'image/jpeg'
         f.write("<item id=\"img_" + str(uniqueid) + "\" href=\"" + folder + "/" + path[1] + "\" media-type=\"" +
@@ -1418,6 +1420,8 @@ def makeParser():
                                     help="Create PNG files instead JPEG for black and white images")
     processing_options.add_argument("--force-png-rgb", action="store_true", dest="force_png_rgb", default=False,
                                     help="Force color images to be saved as PNG")
+    processing_options.add_argument("--webp", action="store_true", dest="webp", default=False,
+                                    help="Replace JPG with lossy WEBP and PNG with lossless WEBP")
     processing_options.add_argument("--pnglegacy", action="store_true", dest="pnglegacy", default=False,
                                     help="Use a more compatible 8 bit png instead of 4 bit")
     processing_options.add_argument("--noquantize", action="store_true", dest="noquantize", default=False,
@@ -1537,6 +1541,8 @@ def checkOptions(options):
     options.kindle_azw3 = options.iskindle and ('MOBI' in options.format or 'EPUB' in options.format)
     options.kindle_scribe_azw3 = options.profile.startswith('KS') and options.kindle_azw3
 
+    options.webp_output = options.format != 'PDF' and not options.kindle_azw3 and options.webp
+
     # CBZ files on Kindle DX/DXG support higher resolution
     if options.profile == 'KDX' and options.format == 'CBZ':
         options.profileData = list(image.ProfileData.Profiles[options.profile])