Sometimes I see questions about whether DPP software can upscale an image.
The answer is yes that if one checks the resize box in the save dialog, then DPP is willing to upscale up to 300%. As a general rule, I think it is unwise to upscale more than 200%, but I did 300% to illustrate the process.
The upscale algorithm used by DPP does not seem to me as good as the algorithm used by GraphicsMagick.
I made a photo of a deer outside a window at our house and noticed that there was a reflection of the house in the eye of the deer. "White-tailed Deer (Odocoileus virginianus) in Norman, Oklahoma, United States on January 6, 2025"
As displayed here, the images have once again been scaled by some unknown algorithm. More about image scaling is at https://en.wikipedia.org/wiki/Image_scaling
One advantage to using GraphicsMagick instead of DPP to upscale an image, is that after upscaling one should do an additional unsharp mask. More about unsharp masking is at https://en.wikipedia.org/wiki/Unsharp_masking
First, version I published on my webserver at: https://www.rsok.com/~jrm/2025Jan15_birds_and_cats/2025jan06_deer_IMG_2544c.html
second, version saved as 16 bit TIF from DPP, converted to 16 bit PNG by GraphicsMagick, and compressed by jpegli compiled from Google source code to get it under 5MB for upload to this forum:
Next, cropped and upscaled by DPP
Next, upscaled 300% by GraphicsMagick
Some of the command lines I used:
gm convert -verbose IMG_2544c.JPG -resize "25%" -unsharp 0x1 -mattecolor black -frame 16x16 -font helvetica -fill white -font '/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf' -draw "text 4,1228 'White-tailed Deer (Odocoileus virginianus) in Norman, Oklahoma, United States on January 6, 2025, Copyright http://www.rsok.com/~jrm/ All rights reserved.'" -define 'jpeg:dct-method=float,jpeg:optimize-coding=true' -interlace line -quality 97 2025jan06_deer_IMG_2544c.jpg gm convert -verbose IMG_2544c.TIF -depth 16 IMG_2544cs3.png /home/jrm/src/libjxl/build2/tools/cjpegli -v -q 85 IMG_2544cs3.png IMG_2544cxlis.JPG exiftool -tagsfromfile IMG_2544c.JPG IMG_2544cxlis.JPG gm convert -verbose IMG_2544cs5s.JPG -resize "300%" -unsharp 0x1 -define 'jpeg:dct-method=float,jpeg:optimize-coding=true' -interlace line -quality 90 IMG_2544cs5x3.JPG exiftool -tagsfromfile IMG_2544c.JPG IMG_2544cs5x3.JPG
