Image Editing

GIMP, More Awesome Than I Remember

Shawn Powers — Mon, 23 Oct 2017 11:24:19 +0000

For what seems like decades, GIMP (Graphic Image Manipulation Program) has been the de facto standard image editor for Linux. It works well, has many features, and it even supports scripting. I always have found it a bit clumsy, however, and I preferred using something else for day-to-day work. I recently had the pleasure of sitting at a computer without an image editor though, so I figured I'd give GIMP another try on a non-Linux operating system. See, the last time I tried to use GIMP on OS X, it required non-standard libraries and home-brew adding. Now, if you head over to the GIMP site, you can download a fully native version of GIMP for Windows, OS X and Linux.

I'll be honest, just being able to install GIMP with a simple drag and drop on OS X was an improvement worth noting. When I actually started using it, however, I found that it's truly as powerful as Photoshop for the things I do. Granted, Photoshop likely has features advanced users might need that GIMP doesn't have, but everything I do with images was fully supported without exception. In the screenshot (from an OS X machine), you can see an example of me "painting" my Volkswagen using nothing more than the auto-selection tool and a virtual airbrush.

If you're looking for a great graphic editor and want to be consistent across platforms, GIMP is truly hard to beat. And if you tried it years ago but didn't really care for it, I urge you to give it another try. I'm shocked at how well it works, even on platforms other than Linux!

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Watermarking Images--from the Command Line

Dave Taylor — Tue, 12 Sep 2017 13:52:13 +0000

by Dave Taylor

Us geeks mostly think of the command line as the best place for text manipulation. It's a natural with cat, grep and shell scripts. But although you can't necessarily view your results from within a typical terminal window, it turns out to be pretty darn easy to analyze and manipulate images from within a shell script.

In my last article, I introduced the splendid open-source ImageMagick suite that offers more features and functionality than you can shake a tree's worth of branches at. Why you would be shaking a tree at a piece of software escapes me, but, hey, I'm just writing this stuff, not thinking about what I'm saying.

Um...wait a sec.

Anyway, ImageMagick includes a variety of programs that let you analyze, manipulate and even convert image files in a remarkable number of different ways.

My last article described setting things up and a few easy ways to confirm that the suite was working correctly on your computer. Now let's start with a simple task that can be useful for web servers: a script that checks image files and flags any that are more than a specific size.

In fact, let's use 8MB because that's the maximum size allowed in Facebook Open Graph, a fact of which many webmasters are already well aware.

Finding Those Big Darn Image Files

Identifying big files can be done with a simple find, but the goal here is to do something more sophisticated, so let's pair it with the ImageMagick command identify.

Here's a loop to identify files bigger than a specified size:


for name in `find *{png,jpg} -size +8M -print`
do
    echo file $name is bigger than 8MB
done

That's a good start, but for those image files that match, more detail would be helpful, and I'm not talking ls -l output! Instead, let's replace the rudimentary echo statement with something more advanced:


dimensions=$(identify $name | cut -d\  -f3)
size=$(identify $name | cut -d\  -f7)
echo "File $name ($dimensions) has file size $size"

Now let's have a quick test:


$ sh bigimages.sh
File screenshot-6.png (1800x490) has file size 9.639MB
$

It's definitely more informative than just doing an ls -l and particularly so if you were to put this in an automatic email report for hosting clients!

Why? Because lots of people who aren't tech-savvy upload images directly from digital cameras—images that can be enormous. They resize the displayed image in their blog posts, but the original files are way larger than necessary, slowing down their sites unnecessarily.

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Manipulate Images with ImageMagick

Dave Taylor — Thu, 17 Aug 2017 12:05:50 +0000

by Dave Taylor

In my last article, I had some fun looking at the children's game of rock, paper, scissors, writing a simple simulator and finding out that some strategies are better than others. Yes, I used "strategy" and "rock, paper, scissors" in the same sentence!

So for this article, I thought it would be interesting to delve into something more functional and pragmatic: image manipulation. Ordinary shell scripts don't tend to do much with images because you can't display anything from the command line.

But let's be honest here. The chance that you're running Linux or a similar command-line interface raw on a computer terminal is pretty darn low. More likely, you've got a terminal window open on your X11 system or, like I often have, you're running a command-line interface app within a modern OS like Mac OS X. And this means, yes, you do have the ability to display graphics, just not within the terminal app itself.

Get Yourself a Copy of ImageMagick

The first step is to download and install a copy of the ImageMagick suite of graphics-related commands. You already might have it installed if you're lucky: Just type convert -version, and if you have it installed, you'll see something similar to this:


$ convert -version
Version: ImageMagick 6.9.6-6 Q16 x86_64 2016-12-31
 ↪http://www.imagemagick.org
Copyright: Copyright (C) 1999-2016 ImageMagick Studio LLC
License: http://www.imagemagick.org/script/license.php
Features: Cipher DPC Modules
Delegates (built-in): bzlib djvu fftw fontconfig freetype gslib
 ↪jbig jng jp2 jpeg lcms ltdl lzma openexr png ps tiff
 ↪webp x xml zlib

If you don't have it installed, it can be quite a task to get it all up and running. Everything lives here, which is where you want to get started.

On a Linux system, you can use the package manager of choice for your distro. You can grab a compressed tar image from the site, or you can use rpm, like this:


rpm -Uvh ImageMagick-7.0.4-1.x86_64.rpm

Of course, there's a bit more to it, but that'll get you started.

On a Mac, you'll want to start by installing MacPorts, which you can't do until you install Xcode (free from Apple, get it through the App Store). Once you've installed Xcode and MacPorts, you can install ImageMagick, and you're good to go.

You know you're good to go when the test command convert -version returns something meaningful. As always, when you install new software, you'll want to log out and log in again for the PATH changes and shell command-line hash to include all the newest programs.

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Resizing Images with ImageMagick

Dave Taylor — Thu, 29 May 2014 19:55:01 +0000

by Dave Taylor

Sure, you can open up a graphics program like GIMP and resize an image, but what if you want to resize 10, 50 or 200 images? ImageMagick's convert program is just what you need.

I a previous article, I started a series on working with ImageMagick on the command line, but then I had to stop and deal with the massive migration project of moving my AskDaveTaylor.com site from one server to another while simultaneously dropping it into a completely different back-end software system—madness. I'm still fixing things and cleaning up the insane sprawl of it all.

So, my last article detoured into a discussion of scripts that helped with the migration process. I'm still working on these fast, short scripts, including one I wrote this morning:


for entry in blog/*
do
  new=$(echo $entry | sed 's/blog\///')
  echo "Redirect 301 $entry $new"
done

Can you track what this loop does? The only tricky part is the new=statement that removes blog/ from the filename matched in the for statement; otherwise, it's quite straightforward.

Seriously though, let's return to ImageMagick. There are a ton of things you can do with the command-line utilities. But first, let me look at where I left off.

I'd just shown a simple example of ImageMagick command-line tools to identify the dimensions of an image and use that as the basis of coming up with a scaled HTML img tag. Here's the script:


#!/bin/sh
identify=/usr/bin/identify
scale=$1
image=$2   # needs input validation code

height=$($identify $image | cut -d\   -f3 | cut -dx -f1)
width=$($identify $image | cut -d\   -f3 | cut -dx -f2)
newwidth="$(echo $width \* $scale | bc | cut -d. -f1)"
newheight="$(echo $height \* $scale | bc | cut -d. -f1)"
echo ""
exit 0

(Actually, I couldn't resist tweaking it slightly if you are keeping track, but I'm still being lazy and not validating the input as of yet. You can add that code easily enough.)

In use:


$ scaledown.sh 0.5 pvp.jpg

Okay, that's one way to make the display of the image be reduced on a Web page, but anyone who has done any work trying to speed up a Web site knows the huge problem here: reducing the container that displays an image doesn't reduce the image. The Web site visitor still has to download the original image, which is a huge waste of bandwidth and a performance hit.

So let's update the script to create a new, smaller version of the image as part of its output.

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GIMP Shmimp, Give Me a Browser

Shawn Powers — Fri, 13 Dec 2013 17:48:59 +0000

by Shawn Powers

Don't get me wrong, I love The GIMP. We all love The GIMP, as our Readers' Choice awards show this month. If I'm being completely honest, however, I rarely have the need for such a powerful application. Usually, regardless of what computer system I'm on, I pick Pixlr as my image editing program.

Pixlr is a Web-based image editing tool that rivals native applications in speed, and more important, in functionality. Powerful tools like "spot heal" that aren't found in most simple image editors are essential for folks like me who still get teenager-like pimples in their late 30s. It also integrates with on-line storage (Flickr, Picasa, Facebook) and allows simple uploads/downloads to your local computer. In fact, you have to look really hard in order to realize Pixlr isn't a native application.

Regardless of what operating system you're on, you can check out Pixlr right now by heading to http://pixlr.com/editor. It's not GIMP, but it certainly isn't gimpy either.

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