Thumbnailator is a Java class library used to generate image thumbnails. It can generate image thumbnails through very simple code, or it can directly generate thumbnails for images in an entire directory.
With this thing, you don't have to bother using Image I/O API, Java 2D API, etc. to generate thumbnails.
Thumbnailator is a third-party library for generating high-quality thumbnails in java, which can be used to
1. Generate a thumbnail image;
2. Add watermark;
3. Picture rotation;
4. Image size scaling;
5. Image compression;
1. Reset the image size
/**
* reset image size
* @throws IOException
*/
Thumbnails.of(new File("原图.jpg"))
.size(160, 160)
.toFile(new File("新图.jpg"));
Generate thumbnails for all images in a folder
Thumbnails.of(new File("path/to/directory")
.listFiles())
.size(640, 480)
.outputFormat("jpg")
.toFiles(Rename.PREFIX_DOT_THUMBNAIL);
Thumbnails.of("Path to original image file")
.scale(1f)
.outputQuality(0.5f)
.toFile("Path to the compressed file");
The scale is the size of the image that can be specified. The value is between 0 and 1. 1f is the size of the original image, and 0.5 is half the size of the original image. The size here refers to the length and width of the image.
The outputQuality is the quality of the image, and the value is also in the range of 0 to 1. The closer to 1, the better the quality, and the closer to 0, the worse the quality.
Create a thumbnail from an image file
Thumbnails.of(new File("original.jpg"))
.size(160, 160)
.toFile(new File("thumbnail.jpg"));
In this example, the image from original.jpg is resized, and then saved to thumbnail.jpg.
Alternatively, Thumbnailator will accept file names as a String. Using File objects to specify image files is not required:
Thumbnails.of("original.jpg")
.size(160, 160)
.toFile("thumbnail.jpg");
This form can be useful when writing quick prototype code, or when Thumbnailator is being used from scripting languages.
Create a thumbnail with rotation and a watermark
Thumbnails.of(new File("original.jpg"))
.size(160, 160)
.rotate(90)
.watermark(Positions.BOTTOM_RIGHT, ImageIO.read(new File("watermark.png")), 0.5f)
.outputQuality(0.8)
.toFile(new File("image-with-watermark.jpg"));
In this example, the image from original.jpg is resized, then rotated to clockwise by 90 degrees, then a watermark is placed at the bottom right-hand corner which is half transparent, then is saved to image-with-watermark.jpg with 80% compression quality settings.
Create a thumbnail and write to an OutputStream
OutputStream os = ...;
Thumbnails.of("large-picture.jpg")
.size(200, 200)
.outputFormat("png")
.toOutputStream(os);
In this example, an image from the file large-picture.jpg is resized to a maximum dimension of 200 x 200 (maintaining the aspect ratio of the original image) and writes the that to the specifiedOutputStream as a PNG image.
Creating fixed-size thumbnails
BufferedImage originalImage = ImageIO.read(new File("original.png"));
BufferedImage thumbnail = Thumbnails.of(originalImage)
.size(200, 200)
.asBufferedImage();
The above code takes an image in originalImage and creates a 200 pixel by 200 pixel thumbnail using and stores the result in thumbnail.
Scaling an image by a given factor
BufferedImage originalImage = ImageIO.read(new File("original.png"));
BufferedImage thumbnail = Thumbnails.of(originalImage)
.scale(0.25)
.asBufferedImage();
The above code takes the image in originalImage and creates a thumbnail that is 25% of the original image, and uses the default scaling technique in order to make the thumbnail which is stored in thumbnail.
Rotating an image when creating a thumbnail
BufferedImage originalImage = ImageIO.read(new File("original.jpg"));
BufferedImage thumbnail = Thumbnails.of(originalImage)
.size(200, 200)
.rotate(90)
.asBufferedImage();
The above code takes the original image and creates a thumbnail which is rotated clockwise by 90 degrees.
Creating a thumbnail with a watermark
BufferedImage originalImage = ImageIO.read(new File("original.jpg"));
BufferedImage watermarkImage = ImageIO.read(new File("watermark.png"));
BufferedImage thumbnail = Thumbnails.of(originalImage)
.size(200, 200)
.watermark(Positions.BOTTOM_RIGHT, watermarkImage, 0.5f)
.asBufferedImage();
As shown, a watermark can be added to an thumbnail by calling the watermark method.
The positioning can be selected from the Positions enum.
The opaqueness (or conversely, transparency) of the thumbnail can be adjusted by changing the last argument, where 0.0f being the thumbnail is completely transparent, and 1.0f being the watermark is completely opaque.
Writing thumbnails to a specific directory
File destinationDir = new File("path/to/output");
Thumbnails.of("apple.jpg", "banana.jpg", "cherry.jpg")
.size(200, 200)
.toFiles(destinationDir, Rename.PREFIX_DOT_THUMBNAIL);
This example will take the source images, and write the thumbnails them as files to destinationDir(path/to/output directory) while renaming them with thumbnail. prepended to the file names.
Therefore, the thumbnails will be written as files in:
path/to/output/thumbnail.apple.jpgpath/to/output/thumbnail.banana.jpgpath/to/output/thumbnail.cherry.jpg
It's also possible to preserve the original filename while writing to a specified directory:
File destinationDir = new File("path/to/output");
Thumbnails.of("apple.jpg", "banana.jpg", "cherry.jpg")
.size(200, 200)
.toFiles(destinationDir, Rename.NO_CHANGE);
In the above code, the thumbnails will be written to:
path/to/output/apple.jpgpath/to/output/banana.jpgpath/to/output/cherry.jpg