- #Imagemagick canvas resize how to
- #Imagemagick canvas resize mac os x
- #Imagemagick canvas resize software
This method takes a block that we pass the source image into. The stamp method calls manipulate! which is a custom CarrierWave method and tells it that we want to use RMagick to generate a PNG image. What we do is loop through a list of colours and make a version for each one. This is all that’s needed to handle the stamped versions. The processing is done in the stamp method. posite!(overlay, 0, 0, Magick:: OverCompositeOp)Ĭolored = Magick:: Image.new( 70, 70) Ĭposite(source.negate, 0, 0, Magick:: CopyOpacit圜ompositeOp) Overlay = Magick:: Image.read( " stamp_overlay.png ").first Source = source.resize_to_fill( 70, 70).quantize( 256, Magick:: GRAYColorspace).contrast( true) Source = Magick:: Image.read( " octocat.png ").first Let’s see what’s involved in using RMagick to generate the same stamp image. It wraps the C library so its interface isn’t always a one-to-one mapping with the command line but it does have a good user guide. This hasn’t been updated recently and some people criticize it for leaking memory but it is a valid option if you’re looking for an alternative to the command-line interface. The interface to both of these gems can be a little cumbersome when we have to deal with extensive image manipulation so keeping the whole command in a string and executing it is often the best way to go. Image Sorcery is a thin wrapper around the command-line too and MiniMagick is similar. There are a couple of gems available that will do just this. One option is just to execute this command from within Ruby and this isn’t such a bad idea. The next step is to get this working in a Rails application. We’ll also crop it to the same dimensions and supply an offset value then save the file as source.png.Ĭonvert -size 70x70 canvas:red \( octocat.png -resize '70x70^' -gravity center -crop '70x70+0+0' -quantize GRAY -colors 256 -contrast stamp_overlay.png -composite -negate \) -compose copy-opacity -composite stamp.png Doing This in a Rails Application We’ll start off in the terminal and resize the image to 70x70 pixels. We’ll use the option with a caret symbol which will allow us to fill the stamp image while maintaining the aspect ratio. This is handy if you’re trying to make a square thumbnail from an oddly-shaped image like we are. Both of these options accept a geometry parameter and the documentation for this tells us the different ways that we can format the argument to change its behaviour. If we look at the documentation for the convert command we’ll see the list of options that can be passed in, including options to crop or resize an image. Our first objective is to resize and crop the source image so that it composites nicely with our overlay texture. In addition to the source image we’ll be working with, which is a PNG of Github’s Octocat, We also have another image, which is an overlay texture made up of a white image with some transparency to give it the appearance of a rubber stamp.
This should give us a convert command, along with several others, for processing images.
#Imagemagick canvas resize mac os x
If you’re running Mac OS X it’s a good idea to use Homebrew to install it as then all that’s needed is to run the command brew install imagemagick. These will give you a good idea of what ImageMagick is capable of and what steps are required to process an image with it. A good place to start is with its command-line tools. If we want to perform image manipulation this can take us quite far.
#Imagemagick canvas resize software
A lot of people have a love-hate relationship with this as it can be difficult to set up and use, although it is a powerful piece of software once it’s up and running.
#Imagemagick canvas resize how to
In this episode we’ll show you how to add this type of image manipulation. We can also choose from a number of colours for our stamp. Whatever image we upload is resized and has effects applied to make it look like a rubber stamp.
The app has a page where we can select from a preset list of stamps or upload an image of our own to turn into a custom stamp. What we’ll focus on in this episode is the ability to customize the stamp.