I need to do the same operations for more than 60 files:
scale image
unsharpen mask
Is it possible to execute this from a script possibly passing the scale value ? I'm on Ubuntu if this could influence the answer.
edit:
What I need to do is to resize some Android icons from 64x64 to 96x96 (as far, maybe other resolutions too).
But these icons have already been blurred so, just increasing the size, I don't get a nice result.
I've seen that if I resize to 96x96 and apply the "Unsharp Mask" filter with the default values (Radius: 5,0 - Amount: 0,50 - Threshold: 0),
I get an acceptable result.
As you are on Ubuntu, you likely already have ImageMagick installed - convert, identify and mogrify commands, amongst others.
So, make a copy of your data and try something like this on a copy:
mogrify -resize 640x480 -unsharp 6x3+1+0 *.jpg
or maybe this
mogrify -resize 1024x768 -sharpen 0x1.0 *.tif
to resize all JPEGs to 640x480 max and sharpen them, and in the second case to resize and sharpen a bunch of TIFFs.
If you specify your GIMP parameters I can probably make closer suggestions.
Related
I have a ps image that I want to convert to a gif image with horizontal by vertical dimensions of 900 and 800 respectively. I have tried to use the command:
convert panel.gs -resize x800 y900 panel.gif
or also:
convert panel.gs -resize 900x800 panel.gif
Can you help me to tweak the convert commands so I can get the desired results?
.gs is not a valid suffix. Did you mean .ps?
Imagemagick will need ghostscript as a delegate. You did not say what was wrong nor what platform or what version of Imagemagick.
If the image does not have the same aspect ratio as the final dimensions you want, you will either 1) need to distort it to fit using !, 2) resize it and then extend to the size you want filling with background color, or 3) resize it with ^ and crop it to the size you want.
convert panel.ps -resize "900x800!" panel.gif
convert panel.ps -resize 900x800 -gravity center -background white -extent 900x800 panel.gif
convert panel.ps -resize "900x800^" -gravity center -extent 900x800 panel.gif
Well, firstly you haven't actually said what's wrong with the two commands that you have tried already.....
Your PostScript program probably does not contain an 'image' as such, PostScript is not a bitmap format its a programming language.
You can use Ghostscript to render the PostScript to an image, and then use ImageMagick to resize that image, possibly you can combine these two steps, or just perform a single conversion, it depends on what exactly you want to happen, which isn't clear.
If (for example) your PostScript program requests a media size of 9 inches by 8 then you can create a bitmap image by simply setting the resolution to 100 dpi using -r100.
If you want the image scaled differently in each direction, then you need to set a non-square resolution. For example if the PostScript program requests media of 9 inches by 4 then you need to set the resolution to 100x200 in order to get an image exactly 900 x 800 pixels. You would use -r100x200 for this.
The alternative, from a PostScript point of view, is to set the media size to a given
value in pixels (using -g900x800) and set -dDFIXEDMEDIA which prevents the PostScript program from changing it. You can then use -dFitPage which will have Ghostscript scale the content to fit the page. However it will scale the content equally in both directions, which may leave white space around the edge.
Now since Ghostscritp doesn't write GIF directly you'll need to load whatever bitmap format you select into IM in order to write it out as a GIF, so perhaps the simplest solution is just to use Ghostscript to render the PostScript to a defined resolution (eg 100 dpi) and then load that image into IM and rescale it there.
Since IM (and therefore convert) use Ghostscript to process PostScript programs, that's what's happening now so it isn't obvious to me what your problem is.
I'm trying to batch convert PDF's to PNG's. Previously, this was always done manually through GIMP by importing a PDF, then converting it to PNG.
With the script that I wrote, this should all be done automatically. But for some reason, the image quality I get from using
convert \
-density 300 \
-adaptive-resize 2048 \
-define png:compression-level=9 \
"File1"
"File2"
Doesn't have the same "quality" compared to doing it via GIMP. See the image below for the difference in image quality.
In GIMP, I don't change much to the image. When I import the PDF, I change the resolution to 2048 pixels. When I convert and export it to PNG, I use all the default values GIMP offers, nothing fancy.
Changing the density to a higher or lower value doesn't do anything to the image. Also changing adaptive-resizing to normal resizing doesn't do much.
In the example image, both pictures are 2048 pixels wide. As you can see the lower image has a lot thicker/blurrier lines.
Example image comparison:
So, I have found a way around my problem.
Increasing the PPI kind of helped but still not as much as I would have liked it to.
Eventually I added this:
-channel A -fx "p*(p>0.2?22:0)"
Just some simple piece of code I found somewhere around here. It checks for the Alpha levels in the picture and if it's below a certain threshold it will just remove or "make the pixel" transparent. If it's over the threshold it will just boost the pixel to maximum visibility. Combined with the high PPI I dont get any "half pixels" anymore.
I searched everywhere but couldn't find an answer to this.
I would like to output all images of a folder in 50Kb exactly and maintain the original aspect ratio.
I tried ImageMagick and resizing to 250x250 e.g but it is not working for me, what it does is change the first dimension and adapt the other, so output images have not the same size.
for image in `ls $#*.jpg`; do
mogrify "${image}" -resize 250x250 "${image}"
done
How do it? Thanks
Updated Answer
If you want the file size of the images to be limited to 50kB, use:
convert input.jpg -define jpeg:extent=50KB output.jpg
Original Answer
Use mogrify, but be careful it will overwrite all your images:
mogrify -resize 250x250! *.jpg
In general, when using mogrify I like to use the -path option to specify an output directory for results, like this to avoid originals getting overwritten:
mkdir results
mogrify -path results ...
Your script will work if you add the ! after the resize which forces the resize even if it distorts the shape of the picture.
If you want a way to do something similar with Python, I wrote an answer that works pretty well here. It does a binary search for a JPEG quality that satisfies a maximum size requirement.
OK, so I have a folder of like 16 images all between the dimensions of 205x150 to 103x148. I want to size them down to the pixel height and width of 25px and stack them horizontally on a transparent background... is that possible?
I should probably be using ImageMagick for this...
You can do all that with ImageMagick.
You're question is not very specific, so here's a quick cheat sheet of command examples that may help you:
# resize image to width 25, keeping aspect ratio
convert -geometry 25x src/image1.png out/image1.png
# resize image to height 25, keeping aspect ratio
convert -geometry x25 src/image1.png out/image1.png
# concatenate images horizontally
convert +append src/image1.png src/image2.png out/image12horiz.png
# concatenate images vertically
convert -append src/image1.png src/image2.png out/image12vert.png
In addition, the montage command is probably perfect to create the final image you are looking for (on a transparent bg with some padding, etc), but I don't remember the syntax.
Another useful command is identify, to find the dimensions of images (along with other details).
After you install ImageMagick, you can see the list of commands in man ImageMagick, and get further details on each command in the man pages. There are an awful lot of functions, but it should not be too difficult to figure out the rest on Google. (I do that all the time.)
Just to add something to #janos answer.
I haven't used previous versions of ImageMagick but on version v6 or later according to the docs http://www.imagemagick.org/Usage/resize/#geometry
Geometry is a very special option. The operator behaves slightly differently in every IM command, and often in special and magical ways. The reasons for this is mostly due to legacy use and should be avoided if at all possible.
So other than the -geometry parameter you can still use -resize and omit the value you want in order to keep the aspect ratio. You can also use the -quality parameter to avoid image quality downgrade when resizing them. Value of quality is between 1 (lowest image quality and highest compression) and 100 (best quality but least effective compression). You can read more here: https://imagemagick.org/script/command-line-options.php#quality
For example:
# resize image to height 25, keeping aspect ratio with quality 90
convert -resize x25 original_image.jpeg -quality 90 resized_image.jpeg
In my application I need to resize and make the quality on PNG files poorer.
In full size the PNGs are 3100x4400px using 2,20MB disk space.
When running the following command:
convert -resize 1400 -quality 10 input.png output.png
the images are resized to 1400x2000 using 5,33MB disk space.
So my question is: How can I reduce the file size?
You can further reduce quality of PNG by using posterization:
https://github.com/pornel/mediancut-posterizer (Mac GUI)
This is a lossy operation that allows zlib to compress better.
Convert image to PNG8 using pngquant.
It reduces images to 256 colors, so quality depends on the type of image, but pngquant makes very good palettes, so you might be surprised how often it works.
Use Zopfli-png or AdvPNG to re-compress images better.
This is lossless and recommended for all images if you have CPU cycles to spare.
After using imagemagick to resize, you can compress the image using pngquant.
On mac (with homebrew) brew install pngquant then:
pngquant <filename.png>
This will create a new image filename-fs8.png that is normally much smaller in size.
Help page says, that -quality option used with PNG sets the compression level for zlib, where (roughly) 0 is the worst compression, 100 - is the best (default is 75). So try to set -quality to 100 or even remove the option.
Another method is to specify PNG:compression-level=N, PNG:compression-strategy=N and PNG:compression-filter=N to achieve even better results.
http://www.imagemagick.org/script/command-line-options.php#quality
For lazy people that arrived here wanting to paste in a one liner:
mogrify -resize 50% -quality 50 *.png && pngquant *.png --ext .png --force
This modifies all of the pngs in the current directory in place, so make sure you have a backup. Modify your resize and quality parameters as suits your needs. I did a quick experiment and mogrify first, then pngquant, resulted in significantly smaller image size.
The ubuntu package for pngquant is called "pngquant" but I had it installed already on 20.04LTS so seems like it may be there by default.
I found that the best way was to use the
- density [value]
parameter.