Reducing scale of png images usually result in bigger file size
Bug #302057 reported by
Silvio Sisto
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| nautilus-image-converter (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned | ||
Bug Description
Binary package hint: nautilus-
When reducing scale of PNG images the resulting image's file size usually is usually larger than the original.
Images I resized were wallpapers of 1280x1024. I resized them to 1024x768.
Original image size was around 400kB and resulting file size was 800kB.
Maybe it has something to do with png file compression.
Revision history for this message
| Andrew McCarthy (andrewmccarthy) wrote | #1 |
| Changed in nautilus-image-converter: | |
| status: | New → Confirmed |
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The resize is achieved by using ImageMagick to run
convert <originalfile> -resize <newsize> <newfile>
As noted on this page:
http://
resizing causes the image to change to 16-bit, probably from 8-bit (run "identify filename.png" at a command prompt to see). I can see why this is done - as the image is shrunk, pixels are merged and new colours created. However, this makes the file larger.
Perhaps the tool should include an option that causes the output to have the same depth as the input? The original image's depth can be determined with:
"identify -format '%[depth]' filename.png"
which outputs a single integer.