imgscalr - Java Image-Scaling LibraryChangelog---------4.2* Added support for a new Method.ULTRA_QUALITY scaling method.This new method uses 3.5x more incremental steps when scaling an image downthan the QUALITY method, providing a much more accurate result. This isespecially noticeable in thumbnails that have diagonal lines that get jaggedduring down-sizing with QUALITY or lower methods.The quality of the ULTRA_QUALITY scaling method is almost on par with theimage resize functionality built into Mac OS X; that is to say it is betterthan GIMP's Lancsoz3 and Windows 7 built-in resize.#61* Fixed subtle bug with incremental scaling and Mode.FIT_EXACT causing theincremental scaling to stop too soon resulting in the wrong-sized resultimage.The stop-condition for incremental scaling assumed that in every case thewidth AND height would be shrinking each iteration; when using Mode.FIT_EXACT this is not necessarily true as one dimension may not changeat all or stop changing before another.#65 4.1* Fixed NullPointerException that occurred when debugging was enabled#60Required a patch-release due to the show-stopping nature of the bug.4.0* [BREAKING] Package has changed from com.thebuzzmedia.imgscalr to org.imgscalr - I am sorry for the inconvenience of this, but this isnecessary. There will be a family of imgscalr-based Java utilities comingout in the future (ExifTool is next) that will all be under this umbrella.* [BREAKING] Java 6 is now required for using imgscalr. The reason for this is because imgscalr includes specific types of ResizeOp and ColorConvertOps that actually segfault the latest Java 5 VM when applied, but run fine in Java 6 and 7.imgscalr cannot knowingly ship VM-segfaulting code that could would introduce a potentiallydevastating situation into client applications.This decision was not made lightly, but with Java 5 end-of-lifed and Java 6being out for 5 years, it seemed like a reasonable requirement.* [BREAKING] Rotation enum was totally redefined. All rotations were redefined in terms of 90,180,270 quadrant rotations as well as h/v FLIP.* [BREAKING] All resize(...) methods that accepted Rotation enums are removed. All graphic operations are now separate and discrete, but can beeasily combined when multiple effects are wanted.* Added apply() support for applying an arbitrary list of BufferedImageOpsSAFELY and efficiently working around all the bugs in the JDK pertainingto BufferedImageOps (also used internally when applying any optionally specified ops).* Added crop() support.* Added pad() support.* Added rotate() support.* All graphic operations (even new ones) were modified to allow the application of 1 or more BufferedImageOps to a final image result beforereturning it for convenience.* Support for all the new operations (apply, crop, pad, rotate) were all added to AsyncScalr so these operations can all be asynchronously performed as well.* Added support for horizontal and vertical flipping of the image via theRotation enum and new rotate() method.* Added pre-defined OP_DARKER and OP_BRIGHTER operations that can be appliedto any image to make them darker or brighter (respectively) by 10%.* Added Mode.FIT_EXACT to support (for the first time) scaling images forced into a specific given dimension instead of honoring the image'sorientation and proportions automatically. * AsyncScalr's use of ExecutorService was rewritten; no more support forpassing in custom ExecutorService implementations or modifying existing oneson the fly and having the class do something magic to them under thecovers (that was bad) -- just extend the class and specify your own logic.* AsyncScalr can be easily customized now through a single method:- createService()  OR- createService(ThreadFactory)* AsyncScalr provides two custom ThreadFactory implementations for subclassesto use if they want to customize the types of Threads generated and used internally for async scale operations.- DefaultThreadFactory creates default threads with all default settings.- ServerThreadFactory generates threads that are optimized to execute in  a server environment (daemon threads w/ LOW_PRIORITY).* AsyncScalr.DEFAULT_THREAD_COUNT was removed and replaced with THREAD_COUNTthat can be customized and set via system properties.* AsyncScalr.THREAD_COUNT's property name was separated into a String constantto make it easier to work with.* Simplified the resize() calls as a result of making all operations discrete;8 duplicate methods accepting "rotation" arguments were removed.* Optimized the application of BufferedImageOps.* Fixed a bug in the application of BufferedImageOps which could have ledto an ImagingOpException bubbling up from native Java2D or a corrupt (black)image for poorly supported image types.* Memory optimized the application of 2 or more BufferedImageOps (interimimages are explicitly cleaned up just like in incremental scaling).* Optimized log() implementation to avoid StringBuilder creation and stringconcatenation. Should be significant run-time savings over time if you arerunning in an environment with debugging turned on.* Removed the identity-return functionality in each method to throw an exception instead of silently returning "src" unchanged.This was done intentionally to avoid users getting caught in the situationwhere they have code that automatically calls flush() on "src" after animgscalr method has returned (assuming they NOW have a modified copy to workwith). In the case of sending in invalid or null arguments, previously imgscalrwould return "src" unchanged, which means the caller would be callingflush() on a perfectly good image they still needed and not a copy as wasassumed by using imgscalr (And there would be no way to tell if imgscalr hadcreated a copy or not without using an == check with EVERY returned imageresult).Instead, invalid or missing arguments passed to any imgscalr method arenow considered an exception so the caller knows IMMEDIATELY when somethingis wrong and won't get magically different/unexpected behavior.* Exposed the potential for every method to fire an ImagingOpException ifone of the BufferedImageOps fails to apply using the hardware-acceleratedunderlying Java2D code path. These exceptions were previously hidden in theguts of Java2D and could bubble up unexpectedly, now they are clearly defineddirectly on the imgscalr API so they can be cause and handled IF the callerwants or needs to do that when using custom BufferedImageOps.* Detailed notations about performance optimizations the caller can make toensure their handling of images are as performant as possible were added toall the methods as a convenience.* Defined DEBUG system property name as a public constant that can be usedto help avoid misspellings when trying to set debugging on.* Modified LOG_PREFIX so it can now be set via the "imgscalr.logPrefix" system property value now.* Rewrote imgscalr test suite to specifically test all discrete operationsand all variations of the operations as well.* Added AllTests test suite so all tests can be easily run at one time toverify the release.* Rewrote Javadoc covering a lot of the return and exception conditions forall the methods to more clearly communicate what is happening inside themethod and to the original images.3.2* Added support for asynchronous & rate-limited scaling operations via theAsyncScalr class.The AsyncScalr class wraps the parent Scalr class and submits scale jobs toan internal ExecutorService. The executor service can be used to serializeand queue up scaling operations to avoid blowing the heap and overloading theunderlying host on a busy, multi-user system (e.g. a web app running imgscalr).AsyncScalr by default uses a fixed-size ThreadPoolExecutor that can be modifiedat run time to any tuned level of threads the caller desires (default 2). Thedefault settings are intended to be safe/efficient to use out of the box on most all systems.Additionally, AsyncScalr can be configured to use *any* ExecutorService implementation passed to it so callers have ultimate control over how the AsyncScalr processes jobs if they need/want it.Typically it is a good idea to roughly map # of Scaling Threads to the # of Cores on the server, especially on a server with plenty of memory and a largeheap for the VM.If you are running inside of a smaller VM heap or lower-memory server (regardlessof core count) you will want to limit the number of simultaneous scale operationsso as not to saturate the heap during scaling when the images are read intointernal BufferedImage instances in VM memory.* Added support for Rotation to the library. You can now specify the followingrotations to be applied to your image:Rotation.NONE - No rotation.Rotation.CLOCKWISE - Clockwise (90 degrees to the right) rotation.Rotation.COUNTER_CLOCKWISE - Counter-clockwise (90 degrees to the left) rotation.Rotation.FLIP - Flip the image (180 degrees rotation).The rotation is performed as tightly and efficiently as possible, explicitlycleaning up temporary resources created during the operation.* API was simplified as duplicate methods without the vararg parameter wereremoved (these were effectively duplicates of the vararg methods make theAPI longer than it needed to be).* Corrected a multitude of incorrect Javadoc comments pertaining to @throwsconditions.* Rewrote the method Javadoc. Manually reviewing uncovered too many copy-pastediscrepancies that left out important information that would be helpful ina  Javadoc popup in an IDE while using imgscalr.* All new code heavily commented.3.1* You can now specify Mode.FIT_TO_WIDTH or Mode.FIT_TO_HEIGHT behaviorswhen resizing an image to get imgscalr to treat one dimension as the primaryand recalculate the other dimension to best fit it, regardless of the image'sorientation. Previously this was decided automatically for you by theorientation of the image.* resize methods now accept 0 or more BufferedImageOps as var-arg arguments.* Workaround for a 10-year-old JDK bug that causes RasterExceptions to getthrown from inside of Java2D when using BufferedImageOps was built directlyinto imgscalr so you don't have to worry about RasterExceptions. Moreinfo here:https://github.com/rkalla/imgscalr/issues/closed#issue/23* API was made more strict and an IAE is thrown if 'src' is null to any ofthe resize operations; a user reported that he spent a while debugging why"imgscalr wasn't working" only to find out it was silently returning due toa null source image. Would have been helpful if imgscalr had notified him ofthe issue immediately.3.0* Big thanks to Magnus Kvalheim fromhttp://www.movellas.com/ for help withthis release!* Support for hardware-accelerated BufferedImageOp's was added to the library.You can now provide an optional BufferedImageOp to many of the methods in theimgscalr library and it will be applied to the resultant image before returningit. * Most common request was for imgscalr to apply an "anti-aliasing" filter toresults before returning them; this was achieved by adding support forBufferedImageOps and providing a hand-tuned ConvolveOp to provide a gooddefault that can be applied easily by folks that want the effect but don'twant to learn all about BufferedImageOps and what "convolve" even means.* Speed/Balance/Quality THRESHOLD values were adjusted for more optimal resultswhen relying on Method.AUTOMATIC to give good-looking results.* Javadoc was updated to clarify hardware acceleration behaviors.2.1* Scaling of certain image types (and byte layouts) could result in very poorlooking scaled images ("pixelated" look, discolored dithering, etc.). This wascorrected by imgscalr forcibly scaling all source images into the most well-supportedimage types by Java2D, resulting in excellent scale result quality regardlessof the Method specified.* The issue of scaling of poorly supported (by Java2D) image-types can lead to unexpectedly poor performance was also corrected as a side-effect of thisbecause all source images are converted to the most commonly supported imagetype for Java2D.2.0* API-break: resize(BufferedImage, Method, int, int, boolean, boolean) was removed andreplaced by resize(BufferedImage, Method, int, int).* DEBUG system variable added; set 'imgscalr.debug' to true to trigger debugging outputin the console. The boolean debug and elapsedTime arguments to the resize methodhave been removed.* New BALANCED method added. Provides a better result than SPEED faster than QUALITY.* Added 2 optimized thresholds (in pixels) that the API uses to select the best Methodfor scaling when the user specifies AUTOMATIC (or doesn't specify a method). This helpsprovide much better results out of the box by default and tightens up the performance of theAPI a bit more.* Image comparison generator utility (ComparisonGenerator test class) added.* Functional portions of API broken into static protected methods that can beeasily overridden by implementors to customize the API without needing to rewritethe resize methods.* Consolidated 5 locations of duplicated rendering code into a single method (scaleImage).* Tightened up image scaling operation to do everything possible to avoid memory leaks (every nativeresource is disposed or released explicitly)* Detailed logging information integrated. If the 'imgscalr.debug' system property istrue, the API outputs exactly what it's doing, what argument values it is processing andhow long it is taking to do each scale operation.* When AUTOMATIC method is specified, the API is more intelligent about selectingSPEED, BALANCED or QUALITY based on the images primary dimension only (more accurate).* Copious amounts of Javadoc added to new methods, new code and existing code. Issues Resolved in 2.0:https://github.com/rkalla/imgscalr/issues/closed1.2* Default proportional-scaling logic is more straight forward. If an image islandscape then width is the preferred dimension and the given height is ignored(and recalculated) and visa-versa if the image is portrait oriented. This givesmuch better "default behavior" results.* Added new convenience method resize(BufferedImage,int,int)* Modified build.xml to output Maven-friendly artifact names.Issues Resolved in 1.2:https://github.com/rkalla/imgscalr/issues/closed1.1* Initial public release.License-------This library is released under the Apache 2 License. See LICENSE.Description-----------A class implementing performant (hardware accelerated), good-looking and intelligent image-scaling algorithms in pure Java 2D. This class implements the Java2D "best practices" when it comes to scaling images as well as Chris Campbell's incremental scaling algorithm proposed as the best method for down-sizes images for use as thumbnails (along with some additional minor optimizations).imgscalr also provides support for applying arbitrary BufferedImageOps againstresultant images directly in the library.TIP: imgscalr provides a default "anti-aliasing" Op that will very lightly softenan image; this was a common request. Check Scalr.OP_ANTIALIASTIP: All resizing operations maintain the original images proportions.TIP: You can ask imgscalr to fit an image to a specific width or height regardless of its orientation using a Mode argument.This class attempts to make scaling images in Java as simple as possible by providinga handful of approaches tuned for scaling as fast as possible or as best-looking as possible and the ability to let the algorithm choose for you to optionally create the best-looking scaled image as fast as possible without boring you with the details if you don't want them.Example-------In the simplest use-case where an image needs to be scaled to proportionally fit a specific width (say 150px for a thumbnail) and the class is left to decide which method will look the best, the code would look like this:  BufferedImage srcImage = ImageIO.read(...); // Load image  BufferedImage scaledImage = Scalr.resize(srcImage, 150); // Scale imageYou could even flatten that out further if you simply wanted to scale the image and write out the scaled result immediately to a single line:  ImageIO.write(Scalr.resize(ImageIO.read(...), 150));Working with GIFs-----------------Java's support for writing GIF is... terrible. In Java 5 is was patent-encumberedwhich made it mostly totally broken. In Java 6 the quantizer used to downsamplecolors to the most accurate 256 colors was fast but inaccurate, yielding poor-looking results. The handling of an alpha channel (transparency) while writingout GIF files (e.g. ImageIO.write(...)) was non-existent in Java 5 and in Java 6would remove the alpha channel completely and replace it with solid BLACK.In Java 7, support for writing out the alpha channel was added but unfortunatelymany of the remaining image operations (like ConvoleOp) still corrupt theresulting image when written out as a GIF.NOTE: Support for scaling animated GIFs don't work at all in any version.My recommendation for working with GIFs is as follows in order of preference:1. Save the resulting BufferedImage from imgscalr as a PNG; it looksbetter as no quantizer needs to be used to cull down the color space and transparency is maintained. 2. If you mostly need GIF, check the resulting BufferedImage.getType() to seeif it is TYPE_INT_RGB (no transparency) or TYPE_INT_ARGB (transparency); if thetype is ARGB, then save the image as a PNG to maintain the alpha channel, if not,you can safely save it as a GIF.3. If you MUST have GIF, upgrade your runtime to Java 7 and save your images asGIF. If you run Java 6, any GIF using transparency will have the transparentchannel replaced with BLACK and in Java 5 I think the images will most all becorrupt/invalid.REMINDER: Even in Java 7, applying some BufferedImageOps (like ConvolveOp) tothe scaled GIF before saving it totally corrupts it; so you would need to avoidthat if you didn't want to save it as a PNG. If you decide to save as a PNG, youcan apply any Ops you want. Troubleshooting---------------Image-manipulation in Java can take more memory than the size of the source imagebecause the image has to be "decoded" into raw ARGB bytes when loaded into theBufferedImage instance; fortunately on most platforms this is a hardware-acceleratedoperation by the video card.If you are running into OutOfMemoryExceptions when using this library (e.g. if youdealing with 10+ MB source images from an ultra-high-MP DSLR) try and up the heap size using the "-Xmx" command line argument to your Java process.An example of how to do this looks like:  java -Xmx128m com.site.MyApp  Reference---------Chris Campbell Incremental Scaling -http://today.java.net/pub/a/today/2007/04/03/perils-of-image-getscaledinstance.htmlRelated Projects----------------ExifTool for Java -https://github.com/rkalla/exiftool