Installation and usage
This is a very basic plugin, that so far encapsulates JAI calls for operations such as image loading, saving, cropping, masking and thumbnail creation.
From the root of your application, call
grails install-plugin http://ricardo.strangevistas.net/dev/grails-image-tools-1.0.zip
All plugin dependencies - two JAI libraries - will be included.
Once the plugin has been installed in your project you'll have a new class at your disposal, called ImageTool. You can use an instance of this class to load an image, operate on it, and save the result.
// To load an image from a buffer def imageTool = new ImageTool() imageTool.load(f.getBytes()) // To load an image from a path imageTool.load("/path/to/image.jpg")
You can save an in-memory snapshot of the image before applying any operations.
imageTool.saveOriginal()
Once loaded, the image can be resized by calling:
imageTool.thumbnail(640) // With the desired thumbnail size
And then the resulting image can be saved to a file calling
imageTool.writeResult("smaller.640.jpg", "JPEG")
An important note is that the loaded image is never explicitly replaced after an operation - instead, a resulting image is created in the object. If you wish to apply more operations to the result, you should swap it with the originally loaded image.
imageTool.swapSource()
There are three functions that you use in order to apply an alpha mask to an image: first you load the alpha and the mask, and then apply them.
imageTool.loadAlpha("alpha.jpg") imageTool.loadMask("mask.jpg") imageTool.applyMask()
Easy enough, isn't it? Let's go for a more complex example. Suppose you want to load an image, reduce it to a maximum size of 640, crop it to a square, then create thumbnails in several sizes and apply masks that have the name "Alpha_XYZ.jpg" and "Mask_XYZ.jpg", where XYZ is the thumbnail size. This is how you would do it:
def imageTool = new ImageTool() imageTool.load("/path/to/image.jpg") // Reduces the image size imageTool.thumbnail(640) // Saves the result imageTool.writeResult("image_smaller.jpg", "JPEG") // Crops it to a square imageTool.square() /* * Swaps the resulting image with the main one, so that we continue to * operate on the square crop. */ imageTool.swapSource() // Creates a copy of the original for later restore imageTool.saveOriginal() /* * Iterate through the thumbnail sizes that we want * */ [178, 133, 69].each { def tempName = "image.${it}.jpg" /* * Creates and saves the thumbnail. It needs to be temporarily saved * and re-loaded before applying the masking operation, because of * something that seems to be a JAI glitch. * See the following link for details: * http://ricardo.strangevistas.net/jai-and-masking-operations.html */ imageTool.thumbnail(it) imageTool.writeResult(tempName, "JPEG") imageTool.load(tempName) // Loads the alpha and mask, and applies them imageTool.loadAlpha("Alpha_${it}.jpg") imageTool.loadMask("Mask_${it}.jpg") imageTool.applyMask() // Finally, save it and restore the original so that we can continue // to operate on the unmodified image imageTool.writeResult(tempname, "JPEG") imageTool.restoreOriginal() }
That's all for now, folks. Grab me on the Grails list or at ricardo at arquetipos dot co dot cr if you need any more pointers. Good luck!
FAQs
mediaLib accelerator
ImageTools uses JAI for its image-handling operations. JAI can use an optional native library for extra performance, or can work in pure Java mode, but if the native library is not present you might get an exception like the following:.
Error: Could not find mediaLib accelerator wrapper classes. Continuing in pure Java mode Occurs in: com.sun.media.jai.mlib.MediaLibAccessor java.lang.NoClassDefFoundError: com/sun/medialib/mlib/Image at com.sun.media.jai.mlib.MediaLibAccessor$1.run(MediaLibAccessor.java:248)
This only means that the native libraries weren't found, and you can still use the ImageTools plugin like you would expect. To see how to get rid of this error, or learn more about JAI's native support, read this thread.
