bash script to resize each image in a directory

xeyve · 04-15-2012, 12:02 PM

Hi everyone, I'm a bit noobish with scripting and I want to automate the hard and long work that is the mannually resize hundreds of image with GIMP. For those that are interested I do that because I want to resize a texture pack for minecraft.

There is many thing I don't really know how to do and for those I need a bit of help, so here are some of theme:

I need to pass sucesively on each image in the directory himself and in directory that are inside the main one. Some time the image are even in a third or fourth directory
I need to know the size of the image so I can resize it with the correcte ratio. I have thincked about using imagemagick's identify command, but then I don't know how to get the size out of the output. Maybe using awk or somthing.
Sometime the image sizes are not perfect ( 513x512 insted of 512x512), so it would be great to be able to round the size up
I aslo need to copy the output (after the image is resized) in another directory but I also need to keep the same hierarchy.

I dont't know if I'm clear so here a exemple: input_pack/item/mod/TC2/dirt_block.png need to be resized and copied in outpout_pack/item/mod/TC2/dirt_block.png

Thanks in advence for your help and if I have new probleme I'll probably come back and ask my question here

pan64 · 04-15-2012, 12:22 PM

this is not the bash. You need a graphical tool to do this. Bash can only be used to collect filenames and start the process.
For example ufraw can resize the picture to a given size (ratio depends on the longer side) and also you can define an output folder. I recommend you to search/google for "batch resize images" or similar, do not try to implement it in awk.

H_TeXMeX_H · 04-15-2012, 12:39 PM

Quote:

Originally Posted by pan64

this is not the bash. You need a graphical tool to do this. Bash can only be used to collect filenames and start the process.
For example ufraw can resize the picture to a given size (ratio depends on the longer side) and also you can define an output folder. I recommend you to search/google for "batch resize images" or similar, do not try to implement it in awk.

Sorry, but you are wrong, you can do this completely in bash.

I'm not gonna write it all for you tho, because it is tedious and you didn't provide enough info on what exactly needs to be done. However, here are some possibly useful commands or algorithms.

You can get the size of a png like:

Code:

identify 800px-Bridge-fan-cable-stayed.svg.png | awk '{ print $3}'

See:
http://imagemagick.org/script/comman...hnbn5#geometry
for geometry options on resizing.

For finding the files and executing commands on them:
http://www.grymoire.com/Unix/Find.html#uh-13

If you need it, there is a GIMP plugin for batch processing:
http://members.ozemail.com.au/~hodsond/dbp.html

xeyve · 04-15-2012, 12:44 PM

I don't need any graphical tool other then imagemagick and I just need to pars the image size out of the output of the identify command. Also, I don't want to use batch I want to write a bash script
I don't want to implement anythingin awk, I just want to use it to pars an output.

What do you mean by this is not the bash ?

EDIT:
Thanks TeXMeX this is exactly what I needed. Could you explain the "awk '{ print $3}'" ?

H_TeXMeX_H · 04-15-2012, 01:45 PM

You can also use cut:

Code:

identify image.png | cut -d' ' -f 3

It prints field 3 separated by white space. I prefer awk because it takes any white space, while cut only takes one type.

If you post more specific things, I may write the script for you if I have time.

xeyve · 04-15-2012, 01:46 PM

I have a new probleme

Here what I have done so far :

Code:

#! /bin/sh

INPUT_DIR=/home/xeyve/DATA/Document/Minecraft/texture\ pack/Sphax
OUTPOUT_DIR=/home/xeyve/DATA/Document/Minecraft/texture\pack/Sphax\ 32
INPUT_SIZE=128
OUTPOUT_SIZE= 32 


RATIO= $($INPUT_SIZE/$OUTPOUT_SIZE)

cd "$INPUT_DIR"

for file in $(find |grep .png)
do
SIZE=$(identify $file |awk '{ print $3}')
# problem here, I can't divide  the string "2048x2048"(exemple) by 4. I need to convert it to  a number, divide it then convert it back to a string. 
RESIZE= $($SIZE/$RATON)
convert $file --resize $RESIZE
done

the awk's output is a string in the format of "128x128" or "1024x1024". I need to devide those number by the ration ( 4 this time ) and then pass the new string to the convert command. The new string should look like "32x32" or "256x256" for the to exemple I have given.

pan64 · 04-15-2012, 01:59 PM

Quote:

Originally Posted by xeyve

What do you mean by this is not the bash ?

I just wanted to say: this is not the optimal solution, bash is not planned to do such things, and again, bash itself is unable to do that (or really hard to implement it).
So you need to use some additional tools, like awk, perl, cut, identify or whatever you know or you find useful. From my point of view (and you do not need to agree) it can be solved easily by an image manipulation tool which has batch processing capabilities. I have a lot of pictures (those are made with a nikon) and I wanted to resize them (and I also modified other things, like brightness). ImageMagick's convert is a good command line tool for this, but maybe not suitable for you.

colucix · 04-15-2012, 02:25 PM

Quote:

Originally Posted by xeyve

the awk's output is a string in the format of "128x128" or "1024x1024". I need to devide those number by the ration ( 4 this time ) and then pass the new string to the convert command. The new string should look like "32x32" or "256x256" for the to exemple I have given.

Code:

RESIZE=$(echo $SIZE | awk -Fx '{print $1/4 FS $2/4}')

Some manuals worth to read:
http://www.grymoire.com/Unix/Awk.html
http://www.gnu.org/software/gawk/manual/ (this is the official GNU awk guide)

xeyve · 04-15-2012, 02:26 PM

well maybe It's not optimal but I also do it for the fun of learning, so it doesn't rellay matter.
I have solved the string to number conversion but now I am unable to convert it back to a string.

Quote:

#! /bin/sh

INPUT_DIR=/home/xeyve/DATA/Document/Minecraft/texture_pack/Sphax
OUTPOUT_DIR=/home/xeyve/DATA/Document/Minecraft/texture_pack/Sphax\ 32
INPUT_SIZE=128
OUTPOUT_SIZE=32

let "RATIO = $INPUT_SIZE / $OUTPOUT_SIZE"
#echo $RATIO

for file in $(find "$INPUT_DIR"|grep .png)
do

SIZE=$(identify $file |awk '{print $3}' |cut -d 'x' -f 2 )
let "RESIZE = $SIZE / $RATIO"
#STRING="$RESIZEx$RESIZE"
#this line doesn't work and I don't know any other way to do it
echo $STRING

done

colucix · 04-15-2012, 02:33 PM

Code:

#STRING="$RESIZEx$RESIZE"
#this line doesn't work and I don't know any other way to do it

This is because the x is a valid character in a variable name, so that bash tries to reference the value of a variable named "RESIZEx". Use braces to embed the variable name (this is the correct bash syntax):

Code:

STRING="${RESIZE}x${RESIZE}

Moreover you don't need to use cut to manage the output from awk:

Code:

STRING=$(identify $file | awk -v ratio=$RATIO '{split($3,a,"x"); print a[1]/ratio "x" a[2]/ratio}')

Check the links in my previous post to learn details about this powerful tool.

Nominal Animal · 04-15-2012, 02:40 PM

@colucix: Wouldn't it be better to make sure the result is an integer? Maybe printf("%.0fx%.0f\n", a[1]/ratio, a[2]/ratio) ? The %.0f pattern will print a correctly rounded integer.

colucix · 04-15-2012, 02:42 PM

Of course! Thank you Nominal Animal!

jschiwal · 04-15-2012, 03:26 PM

You can use variable expansion to extract the x and y values.
size="2048x1024"
xsize=${size%x*}; ysize=${size#*x}

Replace the 'x' with [xX:] to cover the 3 forms you might see, 1024x512, 1024X512, 1024:512. You could define functions to hide the details of extracting the dimensions, making the rest of the script easier to read and write.

David the H. · 04-16-2012, 12:56 AM

I don't have time now to really read this thread, but you might want to look through this list of preexisting imagemagick scripts. There may be one that does exactly what you want.

http://www.fmwconcepts.com/imagemagick/index.php

PS: Please use [code][/code] tags around your code and data, to preserve formatting and to improve readability. Please do not use quote tags, colors, or other fancy formatting.

H_TeXMeX_H · 04-16-2012, 02:33 AM

Just so you know there is a 32x32 texture pack:
http://bdcraft.net/download-purebdcr...-for-minecraft

Also, it's a bit more complicated because many textures are not square and are not 128. For example: 128x2048, 512x256, 512x512.

You should take this into account.