Java2D support for JRuby

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Next
+
+* Add a JRuby-only Java2D/ImageIO processor available as `ImageProcessing::Java2D`
+
 ## 2.0.3 (2026-06-08)
 
 * Prevent remote code execution when operation names come from user input, closing bypasses through the `#operation` meta-builder, `#method_missing`, and nested `#send` calls (reported by @szymonsec)

README.md

@@ -7,6 +7,7 @@ This gem can process images with [ImageMagick] or [libvips]. ImageMagick is a
 good default choice, especially if you are migrating from another gem or library
 that uses ImageMagick. Libvips is a newer library that can process images [very
 rapidly][libvips performance] (often multiple times faster than ImageMagick).
+On JRuby, it can also process images with the Java2D image APIs.
 
 
 ## Goal
@@ -50,9 +51,16 @@ In a Mac terminal:
   gem "ruby-vips", "~> 2.0" # if using libvips
   ```
 
+On JRuby, `ImageProcessing::Java2D` uses only the bundled Java2D image APIs, so
+it needs no additional gem or native library. MiniMagick and Vips can still be
+selected.
+
 
 ## Usage
 
+On JRuby, **[`ImageProcessing::Java2D`]** provides the same chainable API using
+the Java2D image APIs.
+
 Processing is performed through **[`ImageProcessing::Vips`]** or
 **[`ImageProcessing::MiniMagick`]** modules. Both modules share the same
 chainable API for defining the processing pipeline:
@@ -155,6 +163,7 @@ You can continue reading the API documentation for specific modules:
 
 * **[`ImageProcessing::Vips`]**
 * **[`ImageProcessing::MiniMagick`]**
+* **[`ImageProcessing::Java2D`]** (JRuby only; no additional dependency)
 
 See the **[wiki]** for additional "How To" guides for common scenarios. The wiki
 is publicly editable, so you're encouraged to add your own guides.
@@ -219,6 +228,7 @@ The `ImageProcessing::MiniMagick` functionality was extracted from
 [GraphicsMagick]: http://www.graphicsmagick.org
 [`ImageProcessing::Vips`]: doc/vips.md#readme
 [`ImageProcessing::MiniMagick`]: doc/minimagick.md#readme
+[`ImageProcessing::Java2D`]: doc/java2d.md#readme
 [refile-mini_magick]: https://github.com/refile/refile-mini_magick
 [wiki]: https://github.com/janko/image_processing/wiki
 [HTTP.rb]: https://github.com/httprb/http

doc/java2d.md

@@ -0,0 +1,39 @@
+# ImageProcessing::Java2D
+
+`ImageProcessing::Java2D` is a JRuby image processor implemented with the JDK's
+ImageIO and Java2D APIs. It has no native library or additional gem dependency.
+MiniMagick and Vips remain available on JRuby and are not replaced automatically.
+
+## Usage
+
+```rb
+require "image_processing/java2d"
+
+processed = ImageProcessing::Java2D
+  .source(image)
+  .resize_to_limit(400, 400)
+  .convert("png")
+  .call
+```
+
+In Rails, select it with `config.active_storage.variant_processor = :java2d`.
+The canonical Ruby API remains `ImageProcessing::Java2D`.
+
+The processor implements `resize_to_limit`, `resize_to_fit`, `resize_to_fill`,
+`resize_and_pad`, `resize_to_cover`, `crop`, `rotate`, `flip`, `composite`, and
+`strip`. JPEG EXIF orientation is applied on load by default; pass
+`loader(auto_orient: false)` to retain the stored orientation.
+
+The Java2D-specific operation keywords are `gravity` on `resize_to_fill`,
+`background` and `gravity` on `resize_and_pad`, `background` on `rotate`, and
+`mode`, `gravity`, and `offset` on `composite`. Other operation keywords are
+rejected instead of being silently ignored.
+
+Image formats are limited to the ImageIO readers and writers installed in the
+JVM. Standard JDKs include JPEG, PNG, GIF, BMP, and WBMP. The `saver` options
+are `quality` (either `0.0..1.0` or `0..100`), `saver` for an explicit ImageIO
+format name, and `background` for flattening transparent images to JPEG.
+
+`composite` supports the `over`, `src`, `clear`, and `dest-over` modes. Java2D
+does not provide equivalents for every ImageMagick or libvips operation; use
+`custom` to work directly with the `java.awt.image.BufferedImage` accumulator.

image_processing.gemspec

@@ -6,8 +6,8 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 3.0"
 
-  spec.summary       = "High-level wrapper for processing images for the web with ImageMagick or libvips."
-  spec.description   = "High-level wrapper for processing images for the web with ImageMagick or libvips."
+  spec.summary       = "High-level wrapper for processing images for the web with ImageMagick or libvips. Supports Java2D on JRuby."
+  spec.description   = "High-level wrapper for processing images for the web with ImageMagick or libvips. It also supports the Java2D image APIs on JRuby."
   spec.homepage      = "https://github.com/janko/image_processing"
   spec.authors       = ["Janko Marohnić"]
   spec.email         = ["janko.marohnic@gmail.com"]

lib/image_processing.rb

@@ -28,4 +28,7 @@ def self.unsafe_method?(receiver, name)
 
   autoload :MiniMagick, "image_processing/mini_magick"
   autoload :Vips, "image_processing/vips"
+  autoload :Java2D, "image_processing/java2d"
+  # ActiveSupport camelizes the Rails processor name :java2d as Java2d.
+  autoload :Java2d, "image_processing/java2d"
 end