Fastest way of scaling an image (thumbnail generation)

[tomf]

Whats the fastest way of scaling an image? Most images are jpgs, and I don't really care about the quality. It should just be fast.

I tried:

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convert image.jpg -size 256x256 -thumbnail 256x256 output.jpg

but it's much slower (10 times) than for example irfanview. It looks better - yes - but I don't need the quality.

[magick]

Put the -size option before your image filename.

[fmw42]

Also if you use png for the output then jpg compression does not slow things down. The file sizes will be larger. So I am not sure which will be slower, doing the jpg compression or the larger size file writing. You may want to test this and get back to the forum with what you find. I think we would all be interested. Unless someone already knows.

[tomf]

jpg ist faster:

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===  convert -size 256x256 1.jpg -thumbnail 256x256 thumbs/1.jpg ===

Execution time: 0.375 s

Code: Select all

===  convert -size 256x256 1.jpg -thumbnail 256x256 thumbs/1.png ===

Execution time: 0.506 s

The -size argument before the filename makes it faster but not fast enough. Can't I use a simpler scaling-filter?

Here is a picture taken from irfanviews batch conversion:

And here from imagemagick (the quality is better which I don't need)

[magick]

Next up, use -sample instead of -thumbnail.