14 May
2017
14 May
'17
10:29 a.m.
On 14.05.2017 17:55, Mark Trickett via luv-main wrote:
Hello All,
I am wanting to cut the file size of photos from my phone. I have
tried opening in GIMP, but takes a bit of mousing and clicking around,
and even saving/exporting several times to get the size down. I think
the imagemagik suite should be able to do, but my reading of the man
pages does not make it apparent to me. They talk of resizing, but it
looks like the linear extent, rather than loosing some detail of the
same extent of image. I would appreciate any contributions.
regards,
Mark Trickett
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To scale an image in gimp load the image go to menu item "image>Scale
Image"
type in size, press scale. Examine the result. To save use menu item
"File>Export As..."
Close file, a box will come to save or discard file, press discard.
If only doing a small number of images (below say 20) I use this
particularly if accurate size is important, say for desktop
backgrounds..
On the command line when doing work on a lot of images consider the
Netpbm tools, this is a large set of command line tools that will allow
one to do almost ANYTHING with images on the command line, For scaling
images "pnmscale" does the job.....
Note: This is from an uptodate version of Netpbm, I believe the one in
Debian is VERY old.
pnmscale(1) General Commands Manual
pnmscale(1)
NAME
pnmscale - scale a portable anymap
SYNOPSIS
pnmscale scale_factor [pnmfile]
pnmscale -reduce reduction_factor [pnmfile]
pnmscale [{-xsize=cols | -width=cols | -xscale=factor}]
[{-ysize=rows | -height=rows |
-yscale=factor}] [pnmfile]
pnmscale -xysize cols rows [pnmfile]
pnmscale -pixels n [pnmfile]
Miscellaneous options:
-verbose -nomix
Minimum unique abbreviation of option is acceptable. You may use
double hypens instead of
single hyphen to denote options. You may use white space in place
of the equals sign to
separate an option name from its value.
DESCRIPTION
Reads a PBM, PGM, or PPM image as input, scales it by the specified
factor or factors and
produces a PGM or PPM image as output. If the input file is in
color (PPM), the output
will be too, otherwise it will be grayscale (PGM). This is true even
if the input is a
black and white bitmap (PBM), because the process of scaling can
turn a combination of
black and white pixels into a gray pixel.
If you want PBM output, use pgmtopbm to convert pnmscale's output to
PBM. Also consider
pbmreduce.
You can both enlarge (scale factor > 1) and reduce (scale factor <
1).
When you specify an absolute size or scale factor for both
dimensions, pnmscale scales
each dimension independently without consideration of the aspect
ratio.
If you specify one dimension as a pixel size and don't specify the
other dimension, pnm-
scale scales the unspecified dimension to preserve the aspect ratio.
If you specify one dimension as a scale factor and don't specify the
other dimension, pnm-
scale leaves the unspecified dimension unchanged from the input.
If you specify the scale_factor parameter instead of dimension
options, that is the scale
factor for both dimensions. It is equivalent to -xscale=scale_factor
-yscale=scale_factor
.
Specifying the -reduce reduction_factor option is equivalent to
specifying the scale_fac-
tor parameter, where scale_factor is the reciprocal of
reduction_factor.
-xysize specifies a bounding box. pnmscale scales the input
image to the largest size
that fits within the box, while preserving its aspect ratio.
-pixels specifies a maximum total number of output pixels. pnmscale
scales the image down
to that number of pixels. If the input image is already no more
than that many pixels,
pnmscale just copies it as output; pnmscale does not scale up with
-pixels.
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