在java中将PPM转换为JPG或BMP

Question

我需要知道用java编写一个函数来读取ppm文件并将其转换为jpg或bmp格式的可行性。有人有这方面的经验吗？我能够使用ImageMagick等工具实现目标，但我想以纯粹Java的方式做到这一点。

Answer 1

除了旧的Sun JAI实现之外，还有额外的ImageIO插件TwelveMonkeys ImageIO，它们扩展了JDK/JRE中的ImageIO实现。

下面是使用这些插件的小示例。该示例取决于版本 3.1-SNAPSHOT（早期发行版不提供 PNM 支持）。所以你需要先构建插件项目。

./pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>sub.optimal</groupId>
    <artifactId>JAI-Demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>com.twelvemonkeys.imageio</groupId>
            <artifactId>imageio-pnm</artifactId>
            <version>3.1-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>com.twelvemonkeys.imageio</groupId>
            <artifactId>imageio-jpeg</artifactId>
            <version>3.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>
    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.3.2</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>java</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <killAfter>-1</killAfter>
                    <mainClass>sub.optimal.jai.Main</mainClass>
                    <systemProperties>
                        <systemProperty>
                            <key>user.dir</key>
                            <value>${project.build.directory}classes</value>
                        </systemProperty>
                    </systemProperties>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

./src/main/java/sub/optimal/jai/Main.java

package sub.optimal.jai;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import javax.imageio.ImageIO;
/**
 *
 * @author SubOptimal
 */
public class Main {
    public static void main(String[] args) throws IOException {
        String outFormat = "%-17s: %s%n";
        String filesDirectory = System.getProperty("user.dir");
        System.out.printf(outFormat, "files directory", filesDirectory);
        System.out.printf(outFormat, "supported formats", Arrays.toString(ImageIO.getWriterFormatNames()));
        Path inputFile = Paths.get(filesDirectory, "pond.ppm");
        System.out.printf(outFormat, "input file", inputFile.toAbsolutePath());
        InputStream is = Files.newInputStream(inputFile, StandardOpenOption.READ);
        BufferedImage image = ImageIO.read(is);
        File outputFile = Paths.get(filesDirectory, "output.jpg").toAbsolutePath().toFile();
        System.out.printf(outFormat, "output file", outputFile.getAbsolutePath());
        boolean writeSuccess = ImageIO.write(image, "JPEG", outputFile);
        System.out.printf(outFormat, "write successful", writeSuccess);
    }
}

./

src/main/resources/pond.ppm
该文件是 jai-1_1_2-unix-sample 中提供的图像之一.tar.gz

生成并运行示例代码。

mvn clean compile exec:java

Answer 2

我会搜索ImageMagick Application Programmer Interfaces。它们具有每种重要语言的接口。

我发现Java的哲学是广泛研究已经存在的东西，找到满足你需求的最佳解决方案，然后编写与之接口所需的最少代码。这是一种纯粹的Java方式。