com.giraone.imaging.FileTypeDetector Maven / Gradle / Ivy

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Utility JAR for imaging routines, e.g. thumbnail creation for PDF and bitmaps
There is a newer version: 1.2.0
package com.giraone.imaging;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

// TODO: Check, if Apache Tika or implementations of java.nio.FileTypeDetector has more features.

/**
 * A basic file type detection class based on looking for 'magic numbers' or text strings in the file header.
 */
public class FileTypeDetector {

    private static final Logger LOGGER = LogManager.getLogger(FileTypeDetector.class);
    private static final FileTypeDetector _THIS = new FileTypeDetector();

    public static FileTypeDetector getInstance() {
        return _THIS;
    }

    private FileTypeDetector() {
    }

    /**
     * Determine the file type. Return UNKNOWN. if detection fails.
     *
     * @param file a File object
     * @throws IOException on errors opening the file
     */
    public FileType getFileType(File file) throws IOException {
        try (InputStream is = new FileInputStream(file)) {
            return this.getFileType(is);
        }
    }

    /**
     * Determine the file type. Return UNKNOWN, if detection fails.
     *
     * @param filePath a file path string
     * @throws IOException on errors opening the file
     */
    public FileType getFileType(String filePath) throws IOException {
        try (InputStream is = new FileInputStream(filePath)) {
            return this.getFileType(is);
        }
    }

    /**
     * Determine the file type. Return UNKNOWN, if detection fails.
     *
     * @param is an input stream providing the file. The input stream will NOT be closed after processing is done.
     */
    public FileType getFileType(InputStream is) {
        byte[] buf = new byte[132];
        try {
            int r = is.read(buf, 0, 132);
            if (r < 4) return FileType.UNKNOWN;
            is.close();
        } catch (IOException e) {
            LOGGER.error("Error reading input stream", e);
            return FileType.UNKNOWN;
        }

        int b0 = buf[0] & 255;
        int b1 = buf[1] & 255;
        int b2 = buf[2] & 255;
        int b3 = buf[3] & 255;

        // PDF (%PDF-1.X)
        if (b0 == '%' && b1 == 'P' && b2 == 'D' && b3 == 'F')
            return FileType.PDF;

        // PNG
        if (b0 == 137 && b1 == 80 && b2 == 78 && b3 == 71)
            return FileType.PNG;

        // Big-endian TIFF ("MM")
        if (b0 == 73 && b1 == 73 && b2 == 42 && b3 == 0)
            return FileType.TIFF;

        // Little-endian TIFF ("II")
        if (b0 == 77 && b1 == 77 && b2 == 0 && b3 == 42)
            return FileType.TIFF;

        // JPEG
        if (b0 == 255 && b1 == 216 && b2 == 255)
            return FileType.JPEG;

        // GIF ("GIF8")
        if (b0 == 71 && b1 == 73 && b2 == 70 && b3 == 56)
            return FileType.GIF;

        // DICOM ("DICM" at offset 128)
        if (buf[128] == 68 && buf[129] == 73 && buf[130] == 67 && buf[131] == 77) {
            return FileType.DICOM;
        }

        // ACR/NEMA with first tag = 00002,00xx or 00008,00xx
        if ((b0 == 8 || b0 == 2) && b1 == 0 && b3 == 0)
            return FileType.DICOM;

        // PGM ("P2" or "P5")
        if (b0 == 80 && (b1 == 50 || b1 == 53) && (b2 == 10 || b2 == 13 || b2 == 32 || b2 == 9))
            return FileType.PGM;

        // BMP ("BM") - TODO: Not really correct!!! We need && name.endsWith(".bmp")
        if (b0 == 66 && b1 == 77)
            return FileType.BMP;

        return FileType.UNKNOWN;
    }

    public boolean isSupportedImage(FileType fileType) {
        switch (fileType) {
            case JPEG:
            case PNG:
                return true;
            default:
                return false;
        }
    }

    public enum FileType {
        UNKNOWN, JPEG, PNG, TIFF, GIF, BMP, PGM, DICOM, PDF
    }
}