XnView Software

After embedding 192x144 thumbnails in JPEG files with exiftool, XnViewMP reports that the thumbnails are 72x72 pixels. I'm guessing that stops it from using the thumbnails efficiently / without extra processing when its thumbnail size is also set to 192x144. Below are all the commands to reproduce. Or I can stick an example image somewhere if that'd be more useful.

nconvert has the same trouble as XnViewMP.


Run this to create thumbnails:
mkdir thumbtmp
mogrify -path thumbtmp -define jpeg:size=384x288 -auto-orient -background '#eaeaea' -thumbnail '192x144>' -gravity center -extent 192x144 '*.jpg'

ls | grep .jpg$ > IMAGES.txt
while read IMAGE; do
echo "-ThumbnailImage<=thumbtmp/${IMAGE}" > "${IMAGE}.exiftool"
echo "${IMAGE}" >> "${IMAGE}.exiftool"
exiftool -@ "${IMAGE}.exiftool" >> "${IMAGE}.exiftool.err" 2>&1
done < IMAGES.txt


To see problem using different toolchain:

defeat /Volumes/usb3ssd/Stuff/r-photos $ exiv2 -et r-yes.jpg
# This extracts the embedded EXIF thumbnail to r-yes-thumb.jpg


defeat /Volumes/usb3ssd/Stuff/r-photos $ /Applications/nconvert -fullinfo r-yes.jpg
** NCONVERT v6.17 (c) 1991-2011 Pierre-E Gougelet (Sep 17 2012/10:53:49) **
Version for MacOS X (All rights reserved)
** This is a freeware software (for non commercial use)


r-yes.jpg : Success
Format : JPEG TrueColor (v1.1)
Name : jpeg
Compression : JPEG
Width : 1600
Height : 1200
Components per pixel : 3
Bits per component : 8
Depth : 24
# colors : 16777216
Color model : RGB
Bytes Per Plane : 4800
Orientation : Top Left
Xdpi : Not set
Ydpi : Not set
Page(s) : 1
Metadata : ( EXIF )
EXIF:
Camera:
Software (0x0131): Picasa
Image:
EXIF version (0x9000): 02.20
Colour space (0xa001): sRGB
Interoperability offset (0xa005): 112
IOP:
IOP index (0x0001): R98
IOP version (0x0002): 0100
Thumbnail:
Compression (0x0103): 6
X Resolution (0x011a): 72
Y Resolution (0x011b): 72
Resolution unit (0x0128): Inch
Thumbnail offset (0x0201): 236
Thumbnail length (0x0202): 16389


defeat /Volumes/usb3ssd/Stuff/r-photos $ /Applications/nconvert -fullinfo r-yes-thumb.jpg
** NCONVERT v6.17 (c) 1991-2011 Pierre-E Gougelet (Sep 17 2012/10:53:49) **
Version for MacOS X (All rights reserved)
** This is a freeware software (for non commercial use)


r-yes-thumb.jpg : Success
Format : JPEG TrueColor (v1.1)
Name : jpeg
Compression : JPEG
Width : 192
Height : 144
Components per pixel : 3
Bits per component : 8
Depth : 24
# colors : 16777216
Color model : RGB
Bytes Per Plane : 576
Orientation : Top Left
Xdpi : Not set
Ydpi : Not set
Page(s) : 1

Oh nevermind I'm sure that's screen resolution, not image resolution.

Which sadly means my hopes for embedding thumbnails increasing speed are dashed.