I'm surprised your able to see the file types as they are all listed as png. How are you doing that?
I have a homemade script that compares filenames vs their type. Using Cygwin *or any Linux/unix system) the 'file' command will tell you the type, which comes back as bmp, gif, webp (VP7/VP9?), jpeg and png. It also gives details like dimensions, bpp, alpha/transparency, and other details. Though sometimes it's rather bland and only gives 'data' when it doesn't know, or makes assumptions like if it's text or Ascii or utf of some sort.
Regardless, running through my script here is all the files (and the extension they SHOULD be appended). Removed intermediate values to shorten post. If you can fix from the sources then great, if not, converting to png will just make the files larger. the gifs do need to be redone though.
parallaxes/BeerGame2.png.jpg
pictures/Dolly-horse_000.png.webp ... pictures/Dolly-horse_101.png.webp
pictures/Elsy_000.png.webp ... pictures/Elsy_183.png.webp
pictures/frame_00.png.webp ... pictures/frame_59.png.webp
pictures/sasha_000.png.webp ... pictures/sasha_199.png.webp
pictures/vine_00.png.webp ... pictures/vine_59.png.webp
pictures/ElsyBlow1.png.gif ... pictures/ElsyBlow61.png.gif
pictures/KaliArena1.png.gif ... pictures/KaliArena101.png.gif
pictures/KaliBJ0.png.gif ... pictures/KaliBJ80.png.gif
pictures/MariaTent00.png.gif ... pictures/MariaTent100.png.gif
pictures/SashaJerkClean1.png.gif ... pictures/SashaJerkClean42.png.gif
pictures/SashaJerkDirty1.png.gif ... pictures/SashaJerkDirty101.png.gif
pictures/SashaTemple0.png.gif ... pictures/SashaTemple109.png.gif
No objections here.
Using cygwin or a unix environment, a bash file with check_images.txt
In short, it will scan png files and see if it's a PNG, and if it isn't then it will tell you what it actually is.
#!/bin/bash find "$@" -iname "*.png" -print0 | xargs -r -0 file | sed -E "/\.[pP][nN][gG]:\s*PNG/d" find "$@" -iname "*.jpg" -print0 | xargs -r -0 file | sed -E "/\.[jJ][pP][eE]?[gG]:\s*JPEG/d" find "$@" -iname "*.jpg2" -print0 | xargs -r -0 file | sed -E "/\.[jJ][pP][eE]?[gG]:\s*JPEG/d" find "$@" -iname "*.bmp" -print0 | xargs -r -0 file | sed -E "/\.[bB][mM][pP]:\s*PC bitmap/d"
While appending the real extensions (and being able to undo them, i use work/unwork as scripts)
#!/bin/bash T=`check_images.txt "$@"` echo "$T" | grep "JPEG image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1' '\1.jpg'/" >work echo "$T" | grep "PNG image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1' '\1.png'/" >>work echo "$T" | grep "Web/P image" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1' '\1.webp'/" >>work echo "$T" | grep "GIF image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1' '\1.gif'/" >>work echo "$T" | grep "JPEG image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1.jpg' '\1'/" >unwork echo "$T" | grep "PNG image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1.png' '\1'/" >>unwork echo "$T" | grep "Web/P image" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1.webp' '\1'/" >>unwork echo "$T" | grep "GIF image data" | sed -E -e "s:':'\"'\"':g;s/:.*//;s/(.*)/mv '\1.gif' '\1'/" >>unwork