Whoops, I cut/pasted in the wrong snapshot.
Btw, setting "-depth 8", indeed preserves the bit depth but the file
size still grows as significantly as w/o it.
Before conversion
file MD628_1958_AUG_IONOGRAM_3770.png
MD628_1958_AUG_IONOGRAM_3770.png: PNG image data, 4749 x 2368, 8-bit
grayscale, non-interlaced
ls -l MD628_1958_AUG_IONOGRAM_3770.png
-rwxrwxr-x 1 robr robr 5650805 May 21 10:54
MD628_1958_AUG_IONOGRAM_3770.png
After conversion
convert -verbose -rotate 180 -depth 8 -quality 100
MD628_1958_AUG_IONOGRAM_3770.png
MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
MD628_1958_AUG_IONOGRAM_3770.png PNG 4749x2368 4749x2368+0+0
PseudoClass 256c 5.4mb 0.360u 0:02
MD628_1958_AUG_IONOGRAM_3770.png=>MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
PNG 4749x2368 4749x2368+0+0 PseudoClass 256c 6.7mb 1.570u 0:02
file MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png: PNG image data,
4749 x 2368, 8-bit grayscale, non-interlaced
ls -l MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
-rw-rw-r-- 1 robr robr 7007899 May 21 13:26
MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
It doesn't seem to matter too much what I choose for '-quality'.
-quality 0:
convert -verbose -rotate 180 -depth 8 -quality 0
MD628_1958_AUG_IONOGRAM_3770.png
MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png
MD628_1958_AUG_IONOGRAM_3770.png PNG 4749x2368 4749x2368+0+0
PseudoClass 256c 5.4mb 0.360u 0:02
MD628_1958_AUG_IONOGRAM_3770.png=>MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png
PNG 4749x2368 4749x2368+0+0 PseudoClass 256c 6.7mb 1.510u 0:02
file MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png
MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png: PNG image data,
4749 x 2368, 8-bit grayscale, non-interlaced
ls -l MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png
-rw-rw-r-- 1 robr robr 7007907 May 21 13:31
MD628_1958_AUG_IONOGRAM_3770-quality0_rotated.png
+compress for no compression. I'm unsure what this should do
differently than -quality 0 for PNG, but here goes:
convert +compress -verbose -rotate 180 -depth 8
MD628_1958_AUG_IONOGRAM_3770.png
MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png
MD628_1958_AUG_IONOGRAM_3770.png PNG 4749x2368 4749x2368+0+0
PseudoClass 256c 5.4mb
MD628_1958_AUG_IONOGRAM_3770.png=>MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png
PNG 4749x2368 4749x2368+0+0 PseudoClass 256c 6.7mb 1.500u 0:03
file MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png
MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png: PNG image data,
4749 x 2368, 8-bit grayscale, non-interlaced
ls -l MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png
-rw-rw-r-- 1 robr robr 7007907 May 21 13:34
MD628_1958_AUG_IONOGRAM_3770-nocompress_rotated.png
Rob
p.s. Ross, sorry for the double email.
Ross Presser wrote:
> On Wed, May 21, 2008 at 2:04 PM, Rob Redmon <[EMAIL PROTECTED]> wrote:
>
>
>> I'm using 'convert' to rotate PNG images and having trouble in that the
>> file size has grown significantly after the rotation.
>>
>> I start out with an image like:
>> [~/] file MD628_1958_AUG_IONOGRAM_3770.png
>> MD628_1958_AUG_IONOGRAM_3770.png: PNG image data, 4749 x 2368, 8-bit
>> grayscale, non-interlaced
>>
>>
>
> starting as 8-bit grayscale.
>
>
>
>> Unfortunately, the file size has grown ~50%
>> [~/] file MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png
>> MD628_1958_AUG_IONOGRAM_3770-quality100_rotated.png: PNG image data,
>> 4749 x 2368, 16-bit grayscale, non-interlaced
>>
>>
>
> ending as 16-bit grayscale.
>
> You probably have the _16 version of ImageMagick installed. Perhaps the _8
> is needed.
> Greased Lightbox <http://shiftingpixel.com/lightbox/>→←+-↻
>
> Loading image
>
> Click anywhere to cancel
>
> Image unavailable
> _______________________________________________
> Magick-users mailing list
> [email protected]
> http://studio.imagemagick.org/mailman/listinfo/magick-users
>
--
Rob Redmon - Physicist - Ionosphere
NOAA/NGDC
325 Broadway E/GC2
Boulder, Colorado 80305
Tel: (303) 497-4331
Fax: (303) 497-6513
[EMAIL PROTECTED]
"Engineering is the art of making what you want from things you can get."
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