% find . -type f -print0 | xargs -0 -I{} file --mime-type {}
./foo
bar.png: image/png
./OWoHp.png: image/png
./J7ZwV.png: image/png
./foo.txt: inode/x-empty
./bar: inode/x-empty
./hUXnc.png: image/png

% ls foo$'n'bar.png
foo?bar.png

% find . -type f -print0 | xargs -0 -I{} file --mime-type {} | awk -F$"" -F": " '/image/ {print $1}'
bar.png
./OWoHp.png
./J7ZwV.png
./hUXnc.png

% find . -type f -print0 | xargs -0 -I{} file --mime-type {} | awk -F$"" -F":" '/image/ {print $1}' | xargs -I{} identify -format "%[fx:w*h] %in" {}
identify: unable to open image `bar.png': No such file or directory @ error/blob.c/OpenBlob/2709.
identify: unable to open file `bar.png' @ error/png.c/ReadPNGImage/3922.
26696 ./OWoHp.png
47275 ./J7ZwV.png
37975 ./hUXnc.png

./foo
bar.png

find . -type f -exec sh -c 'file --brief --mime-type "$0" |
grep -q ^image/ && identify -format "%[fx:w*h] %in" "$0"' {} ;

exiftool -q -if '$mimetype =~ /image/' -p '$megapixels $directory/$filename' -r .

find . -type f -print0 |
while IFS= read -rd "" filename; do
    type=$( file --brief "$filename" )
    if [[ $type == *image* ]]; then
        identify -format "%[fx:w*h] %in" "$filename"
    fi
done

find . -type f -print0 | while IFS= read -r -d '' file; do
    file --mime-type "$file" | grep -qP "bimage/" &&
        printf '%s %s' $(identify -format '%[fx:w*h]' "$file") "$file";
done | sort -gz | tr '' 'n'
256 ./file 10
256 ./file 15
484 ./file 16
576 ./file 11
576 ./file 17
1024 ./file 12
1024 ./file 19
2304 ./file 13
5625 ./file 14
15190 ./file 2
15680 ./file 1
16384 ./file 9
65536 ./file 18
145200 ./file 0
183531 ./file 6
364807 ./file
3
364807 ./file 4
364807 ./file 5
388245 ./file 8
550560 ./file 7