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Sample for e-paper display with IT8951 controller
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‎examples/epaper_display/README.md‎

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# E-Paper Display
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This sample shows how to communicate with an IT8951 controller for e-paper displays, e.g. [Waveshare E-Ink display HAT for Raspberry Pi](https://www.waveshare.com/9.7inch-e-paper-hat.htm)
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## Prerequisites
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- Java 20
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- Apache Maven
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- 64-bit operating system (macOS, Linux, Windows)
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- IT8951 controller
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On Windows, the display controller's driver must be replaced with the *WinUSB* driver
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using [Zadig](https://zadig.akeo.ie/).
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On macOS, root privileges are required to successfully run the sample. (The standard driver will
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be temporarily detached.)
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## How to run
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### Install Java 20
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Check that *Java 20* is installed:
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```shell
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$ java -version
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```
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If not, download and install it, e.g. from [Azul](https://www.azul.com/downloads/?package=jdk).
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### Install Maven
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Check that *Maven* is installed:
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```shell
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$ mvn -version
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```
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If it is not present, install it, typically using package manager like *Homebrew* on macOS, *Chocolately* on Windows and *apt* on Linux.
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### Run the sample
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```shell
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$ cd JavaDoesUSB/examples/epaper_display
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$ mvn compile exec:exec
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[INFO] Scanning for projects...
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[INFO]
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[INFO] -------------< net.codecrete.usb.examples:epaper-display >--------------
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[INFO] Building epaper-display 0.5.1
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[INFO] from pom.xml
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[INFO] --------------------------------[ jar ]---------------------------------
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[INFO]
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[INFO] --- resources:3.3.1:resources (default-resources) @ epaper-display ---
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[INFO] skip non existing resourceDirectory /Users/me/Documents/JavaDoesUSB/examples/epaper_display/src/main/resources
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[INFO]
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[INFO] --- compiler:3.11.0:compile (default-compile) @ epaper-display ---
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[INFO] Changes detected - recompiling the module! :source
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[INFO] Compiling 2 source files with javac [debug release 20] to target/classes
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[INFO]
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[INFO] --- exec:3.1.0:exec (default-cli) @ epaper-display ---
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Display size: 1200 x 825
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[INFO] ------------------------------------------------------------------------
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[INFO] BUILD SUCCESS
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[INFO] ------------------------------------------------------------------------
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[INFO] Total time: 1.502 s
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[INFO] Finished at: 2023-07-02T14:08:50+02:00
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[INFO] ------------------------------------------------------------------------
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```
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### Run the sample on macOS
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In order to run the sample with root privileges, the best approach is to build it first without
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root privileges and then run it as root without Maven:
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```shell
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$ cd JavaDoesUSB/examples/epaper_display
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$ mvn compile
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[INFO] Scanning for projects...
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...
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[INFO] ------------------------------------------------------------------------
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$ sudo -i
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Password:
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$ cd /Users/me/Documents/JavaDoesUSB/examples/epaper_display
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$ export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-20.jdk/Contents/Home
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$ JAVA_HOME/bin/java --enable-preview --enable-native-access=ALL-UNNAMED -cp target/classes:/Users/me/.m2/repository/net/codecrete/usb/java-does-usb/0.5.1/java-does-usb-0.5.1.jar net.codecrete.usb.examples.EPaperDisplay
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Display size: 1200 x 825
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```

‎examples/epaper_display/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>net.codecrete.usb.examples</groupId>
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<artifactId>epaper-display</artifactId>
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<version>0.5.1</version>
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<name>epaper-display</name>
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<url>https://github.com/manuelbl/JavaDoesUSB/examples/epaper_display</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>20</maven.compiler.source>
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<maven.compiler.target>20</maven.compiler.target>
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</properties>
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<dependencies>
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<dependency>
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<groupId>net.codecrete.usb</groupId>
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<artifactId>java-does-usb</artifactId>
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<version>0.5.1</version>
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</dependency>
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</dependencies>
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<build>
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<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
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<plugins>
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<!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
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<plugin>
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<artifactId>maven-clean-plugin</artifactId>
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<version>3.3.1</version>
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</plugin>
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<!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
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<plugin>
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<artifactId>maven-resources-plugin</artifactId>
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<version>3.3.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.11.0</version>
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<configuration>
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<release>20</release>
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<compilerArgs>
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<arg>--enable-preview</arg>
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</compilerArgs>
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<source>20</source>
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<target>20</target>
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</configuration>
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</plugin>
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<plugin>
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<artifactId>maven-surefire-plugin</artifactId>
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<version>2.22.1</version>
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<configuration>
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<argLine>--enable-preview --enable-native-access=ALL-UNNAMED</argLine>
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</configuration>
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</plugin>
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<plugin>
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<artifactId>maven-jar-plugin</artifactId>
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<version>3.1.2</version>
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</plugin>
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<plugin>
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<artifactId>maven-install-plugin</artifactId>
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<version>3.1.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-deploy-plugin</artifactId>
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<version>3.1.1</version>
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</plugin>
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<!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
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<plugin>
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<artifactId>maven-site-plugin</artifactId>
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<version>3.12.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-project-info-reports-plugin</artifactId>
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<version>3.4.5</version>
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</plugin>
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<plugin>
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<groupId>org.codehaus.mojo</groupId>
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<artifactId>exec-maven-plugin</artifactId>
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<version>3.1.0</version>
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<configuration>
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<executable>java</executable>
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<arguments>
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<argument>--enable-preview</argument>
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<argument>--enable-native-access=ALL-UNNAMED</argument>
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<argument>-classpath</argument>
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<classpath />
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<argument>net.codecrete.usb.examples.EPaperDisplay</argument>
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</arguments>
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</configuration>
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</plugin>
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</plugins>
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</pluginManagement>
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</build>
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</project>

‎examples/epaper_display/src/main/java/net/codecrete/usb/examples/EPaperDisplay.java‎

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//
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// Java Does USB
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// Copyright (c) 2023 Manuel Bleichenbacher
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// Licensed under MIT License
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// https://opensource.org/licenses/MIT
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//
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package net.codecrete.usb.examples;
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import javax.imageio.ImageIO;
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import java.awt.*;
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import java.awt.image.BufferedImage;
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import java.io.File;
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import java.io.IOException;
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/**
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* Example program for displaying an image and text on an e-paper display
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* controlled by an IT8951 controller.
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*/
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public class EPaperDisplay {
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public static void main(String[] args) throws IOException {
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// load image of tiger
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var tigerImage = ImageIO.read(new File("tiger.jpg"));
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// connect to display controller
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var display = new IT8951Driver();
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display.open();
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var width = display.info().width();
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var height = display.info().height();
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System.out.printf("Display size: %d x %d%n", width, height);
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// resize image to fit display (converting it to grayscale)
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var image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
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image = resizedImage(tigerImage, width, height);
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// add text to image
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Graphics2D g = (Graphics2D) image.getGraphics();
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g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
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g.setFont(new Font("Arial", Font.BOLD, 40));
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g.drawString("Java Does USB", 20, height - 40);
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g.dispose();
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// display image
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display.displayImage(image, 0, 0);
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display.close();
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}
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/**
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* Returns a copy of the image, resized to the specified width and height.
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* <p>
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* To prevent distortion, the image is cropped to fit the target width and height.
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* </p>
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* <p>
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* The new image will be in 8-bit grayscale.
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* </p>
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* @param image image to resize
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* @param width width, in pixels
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* @param height height, in pixels
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* @return resized image
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*/
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static BufferedImage resizedImage(BufferedImage image, int width, int height) {
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var resizedImage = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
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var g = (Graphics2D) resizedImage.createGraphics();
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g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
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g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
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g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
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int srcWidth = image.getWidth();
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int srcHeight = image.getHeight();
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var targetAspectRatio = (double) width / height;
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var srcAspectRatio = (double) srcWidth / srcHeight;
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if (targetAspectRatio > srcAspectRatio) {
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// target image is wider than source image - fit width and cut top and bottom
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var modifiedHeight = width / srcAspectRatio;
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var cutY = (int) Math.round((modifiedHeight - height) / 2);
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g.drawImage(image, 0, -cutY, width, height + cutY, 0, 0, srcWidth, srcHeight, null);
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} else {
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// target image is narrower than source image - fit height and cut left and right
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var modifiedWidth = height * srcAspectRatio;
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var cutX = (int) Math.round((modifiedWidth - width) / 2);
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g.drawImage(image, -cutX, 0, width + cutX, height, 0, 0, srcWidth, srcHeight, null);
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}
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g.dispose();
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return resizedImage;
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}
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}

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