“This is my fourth day of participating in the First Challenge 2022. For more details: First Challenge 2022.”
The article brief introduction
Sometimes, our project needs to generate small thumbnails of business pictures, or transcode the picture format, what method will we use?
Use object storage directly and hand over business requirements to third parties? Or do you use javaScript to manipulate images?
Have you tried back-end direct processing?
In this article, you will learn how to use Java to gracefully process images. Including: mainstream image format transcoding, image compression (thumbnail generation), image attached watermark, etc. Main external toolkits used:
- Thumbnailator: The old thumbnail generating tool.
- Webp-imageio-core: Enables Java to support webP reading and writing.
If you want to support more images, you can extend the Java Image IO stream, but more on that later…
Video tutorial
I simply recorded a video, which can be transferred to station B if necessary:
6 minutes Learn how to use Java “hardcore” compression and Transcoding of images – image transcoding and thumbnail generation
Image transcoding/generate thumbnail
The principle of
The Thumbnailator package used this time is actually a encapsulated class and method, which is implemented based on Java Image I/O API, Java 2D API and other API interfaces.
So, based on the Java Image I/O API, the supported Image formats are limited, but they are sufficient for most cases. The supported formats are as follows:
Read: JPEG 2000, JPG, tiff, bmp, PCX, gif, WBMP, PNG, RAW, JPEG, PNM, tif, TIFF, wbmp, jpeg, jbig2, jpg, JPEG2000, BMP, pcx, GIF, png, raw, JBIG2, pnm, TIF, jpeg2000, jpeg 2000Write: JPEG 2000, JPG, tiff, bmp, PCX, gif, WBMP, PNG, RAW, JPEG, PNM, tif, TIFF, wbmp, jpeg, jpg, JPEG2000, BMP, pcx, GIF, png, raw, pnm, TIF, jpeg2000, jpeg 2000
Many of the authors of this article introduced the package and said it supports Apple’s HEIC format, which definitely does not support Thumbnailator processing. Unless you can write a transcoder directly. But in this case, I think it’s better to call ImageMagick. I’ll have a chance to share that later.
How to install
If you are a Maven-managed project, or use Maven-managed projects, add dependencies:
< the dependency > < groupId > net. Coobird < / groupId > < artifactId > thumbnailator < / artifactId > < version > [0.4, < / version 0.5) > < / dependency >Copy the codeThe dependency definition above is in the range of getting version 0.4.xThumbnailatorThe latest available version of. If you need a specific version of the Thumbnailator, replace [0.4, 0.5) with a specific version number, such as 0.4.13
If you are not a Maven project, you can download the latest version of Thumbnailator. How to manually add a lib package to the latest version of Thumbnailator: github.com/coobird/thu…
How to use
Thumbnailator is easy to use. You need to use Java’s Image I/O API, BufferedImages, and Graphics2D to process images. Simple usage demo:
Thumbnails.of(new File("path/to/directory").listFiles())
.size(640, 480)
.outputFormat("jpg")
.toFiles(Rename.PREFIX_DOT_THUMBNAIL);
Copy the code- Original picture address:
path/to/directory - Output image size:
640 * 480 - Output picture format:
jpg - IO stream output address (output picture) :
Rename.PREFIX_DOT_THUMBNAIL
Pictures of transcoding
Demo code:
Thumbnails.of(originalImage).scale(scale)
.outputFormat("jpg")
.outputQuality(compression)
.toFile(thumbnailImage);
Copy the codeAmong them:
scaleIs the picture size equal scale, isfloatType.outputFormatIs the type of output image. Note: This is not supported by defaultwebp, if requiredwebp, need to be installed in advancewebp-imageio-core, you can see below how to make Java supportWebp.outputQualityIs the quality of the output picture, i. e. sharpness/resolution.
Use the original image to generate thumbnails
Demo code:
Thumbnails.of(new File("original.jpg"))
.size(160, 160)
.toFile(new File("thumbnail.jpg"));
Copy the codeWhere, the original image file, can use the String String instead of the address:
Thumbnails.of("original.jpg")
.size(160, 160)
.toFile("thumbnail.jpg");
Copy the codeUsually, thumbnail output is already small, but you can still use.outputQualit to reduce image quality (resolution).
Rotating images
Very simple; Add.rotate. Such as:
Thumbnails.of(new File("original.jpg"))
.rotate(90)
.toFile(new File("image-with-watermark.jpg"));
Copy the codeAdd a watermark
Adding a watermark is also very easy. Add.watermark.
Thumbnails.of(new File("original.jpg")) .watermark(Positions.BOTTOM_RIGHT, ImageIO.read(new File("watermark.png")), 0.5 f). ToFile (new File (" image - with - watermark. JPG "));Copy the codeField demonstration
I use on my website the above packages, set up an online demo address: tool. Mintimate. Cn/processIMG
Function: after the user uploads the picture, the system has the user’s choice of output format, transcoding the picture.
Extension judgment
The front end sends the picture to the background, and the background can judge the file extension:
String thumbnailImageName=originalImage.getName(); // Thumbnail output name String thumbnailImagePath; Switch (format){case "JPG": thumbnailImagePath=System.getProperty("user.dir") + "/file/Output/" + thumbnailImageName.substring(0,thumbnailImageName.lastIndexOf("."))+".jpg"; break; case "PNG": thumbnailImagePath=System.getProperty("user.dir") + "/file/Output/" + thumbnailImageName.substring(0,thumbnailImageName.lastIndexOf("."))+".png"; break; case "WEBP": thumbnailImagePath=System.getProperty("user.dir") + "/file/Output/" + thumbnailImageName.substring(0,thumbnailImageName.lastIndexOf("."))+".webp"; break; case "BMP": thumbnailImagePath=System.getProperty("user.dir") + "/file/Output/" + thumbnailImageName.substring(0,thumbnailImageName.lastIndexOf("."))+".bmp"; break; default: thumbnailImagePath=System.getProperty("user.dir") + "/file/Output/" + thumbnailImageName; break; }Copy the codeCreate a blank thumbnail file
Thumbnailator can create file objects directly from String automatically, but for our own control we’ll create them manually:
File thumbnailImage = new File(thumbnailImagePath);
// Check whether the path exists and create it if it does not
if(! thumbnailImage.getParentFile().exists()) { thumbnailImage.getParentFile().mkdirs(); }Copy the codeTranscoding pictures
try {
switch (format){
case "JPG":
Thumbnails.of(originalImage).scale(scale)
.addFilter(new ThumbnailsImgFilter())
.outputFormat("jpg")
.outputQuality(compression)
.toFile(thumbnailImage);
break;
case "PNG":
Thumbnails.of(originalImage).scale(scale)
.outputFormat("png")
.outputQuality(compression)
.toFile(thumbnailImage);
break;
case "WEBP":
Thumbnails.of(originalImage).scale(scale)
.imageType(ThumbnailParameter.DEFAULT_IMAGE_TYPE)
.outputFormat("webp")
.outputQuality(compression)
.toFile(thumbnailImage);
break;
case "BMP":
Thumbnails.of(originalImage).scale(scale)
.addFilter(new ThumbnailsImgFilter())
.outputFormat("bmp")
.outputQuality(compression)
.toFile(thumbnailImage);
break;
default:
Thumbnails.of(originalImage).scale(scale)
.imageType(ThumbnailParameter.DEFAULT_IMAGE_TYPE)
.outputQuality(compression)
.toFile(thumbnailImage);
break; }}catch (IOException e) {
e.printStackTrace();
}
Copy the codeSince I was using Springboot for a quick build, I actually created a configuration rule called addFilter that renders a transparent PNG image white when it turns into a JPG. (Just to look good…) . Implementation details:
import net.coobird.thumbnailator.filters.ImageFilter;
import java.awt.*;
import java.awt.image.BufferedImage;
public class ThumbnailsImgFilter implements ImageFilter {
@Override
public BufferedImage apply(BufferedImage bufferedImage) {
int w = bufferedImage.getWidth();
int h = bufferedImage.getHeight();
BufferedImage newImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Graphics2D graphic = newImage.createGraphics();
graphic.setColor(Color.white);// Set the background to white
graphic.fillRect(0.0, w, h);
graphic.drawRenderedImage(bufferedImage, null);
graphic.dispose();
returnnewImage; }}Copy the codeIn this way, you can successfully transcode the image (properly, can also compress the image (; ´ Д `)) :
Java handles the Webp format
What is Webp format
According to Wikipedia: WebP (pronounced: Weppy] is a kind of image file format that provides lossless compression and lossless compression (reversible compression) at the same time, derived from image encoding format, is considered to be the sister project of WebM multimedia format, is developed by Google in the purchase of On2 Technologies, released under the TERMS of BSD license. The advantages of Webp are obvious:
- Better image data compression algorithm
- Smaller picture volume
- Naked eye recognition of undifferentiated image quality
- Lossless and lossy compression modes
- Alpha transparency and animation features
Simply put, it can be like PNG format, preserve lossless image quality, and keep the image transparent characteristics; At the same time, the image can be compressed like JPG. Webp, in the same case, has a smaller file size than PNG, and even smaller than JPG.
Webp format is supported
Because Webp was actually developed by Google, Java IO streams were not designed to support the Webp format.
There are many ways for Java IO streams to support Webp, but here is one that has the opportunity to accept more
Depending on the system, you need to install the following dependency packages:
/natives /linux_32 libxxx[-vvv].so /linux_64 libxxx[-vvv].so /osx_32 libxxx[-vvv].dylib /osx_64 libxxx[-vvv].dylib /osx_arm64 libxxx[-vvv].dylib /windows_32 xxx[-vvv].dll /windows_64 xxx[-vvv].dll /aix_32 libxxx[-vvv].so libxxx[-vvv].a /aix_64 libxxx[-vvv].so libxxx[-vvv].aCopy the codeFor reference: github.com/scijava/nat… You can also use webp-imageio-core. Here’s how to use it.
Webp imageio – core is used
Since webp-Imageio-core is not published in the Maven central repository, you need to add your own lib dependencies to the webp-Imageio-core jar package. The jar package can be downloaded at github.com/nintha/webp… Next add a custom
:
<dependency>
<groupId>com.github.nintha</groupId>
<artifactId>webp-imageio-core</artifactId>
<version>{version}</version>
<scope>system</scope>
<systemPath>${pom.basedir}/libs/webp-imageio-core-{version}.jar</systemPath>
</dependency>
Copy the codeFor example: my project, add locallib: 
WebpFormat the picture.
Field use
The simplest use… By adding the Thumbnailator dependencies mentioned above, you can use the Thumbnailator to process the IMAGE IO stream directly. Used alone, we can handle it in the most traditional way: image to WEBP:
public static void main(String args[]){
String srcFile = System.getProperty("user.dir") + "/file/Input/"+"Input.png" // The original address
String webpFile = System.getProperty("user.dir") + "/file/Output/"+"Output.png" // Output address
encodingToWebp(srcFile, webpFile);
}
public static void encodingToWebp(String srcFile, String webpFile) {
encodingToWebp(new File(srcFile),new File(webpFile) );
}
/ * * *@param: srcFile
* @param: webpFile
* @description: Encode the file in WEBP format *@author: Mintimate
*/
public static void encodingToWebp(File srcFile, File webpFile) {
try {
// Obtain an image to encode from somewhere
BufferedImage image = ImageIO.read(srcFile);
// Obtain a WebP ImageWriter instance
ImageWriter writer = ImageIO.getImageWritersByMIMEType("image/webp").next();
// Configure encoding parameters
WebPWriteParam writeParam = new WebPWriteParam(writer.getLocale());
writeParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
writeParam.setCompressionType(writeParam.getCompressionTypes()[WebPWriteParam.LOSSLESS_COMPRESSION]);
// Configure the output on the ImageWriter
writer.setOutput(new FileImageOutputStream(webpFile));
// Encode
writer.write(null.new IIOImage(image, null.null), writeParam);
/ / release of the reader
writer.dispose();
// Close the file stream
fileImageOutputStream.close();
} catch(IOException e) { e.printStackTrace(); }}Copy the codeThe last
At this point, you can use your Thumbnailator to gracefully process your image.
However, you will find that in some cases the image processing (jpeg image processing) will be red, the processing method is very simple, you can use BufferedImage to write and read the image, so that the image will not be red or pink distortion.
There is an opportunity to accept other Java Image IO extensions to allow Java projects to support more image formats.