Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
//License from project: Open Source License 

import java.io.File;
import java.io.FileInputStream;

import java.io.IOException;
import java.io.InputStream;

public class Main {

    public static String getImageType(File file) {
        if (file == null || !file.exists()) {
            return null;
        }
        InputStream in = null;
        try {
            in = new FileInputStream(file);
            return getImageType(in);
        } catch (IOException e) {
            return null;
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static String getImageType(InputStream in) {
        if (in == null) {
            return null;
        }
        try {
            byte[] bytes = new byte[8];
            in.read(bytes);
            return getImageType(bytes);
        } catch (IOException e) {
            return null;
        }
    }

    public static String getImageType(byte[] bytes) {
        if (isJPEG(bytes)) {
            return "image/jpeg";
        }
        if (isGIF(bytes)) {
            return "image/gif";
        }
        if (isPNG(bytes)) {
            return "image/png";
        }
        if (isBMP(bytes)) {
            return "application/x-bmp";
        }
        return null;
    }

    private static boolean isJPEG(byte[] b) {
        if (b.length < 2) {
            return false;
        }
        return (b[0] == (byte) 0xFF) && (b[1] == (byte) 0xD8);
    }

    private static boolean isGIF(byte[] b) {
        if (b.length < 6) {
            return false;
        }
        return b[0] == 'G' && b[1] == 'I' && b[2] == 'F' && b[3] == '8' && (b[4] == '7' || b[4] == '9')
                && b[5] == 'a';
    }

    private static boolean isPNG(byte[] b) {
        if (b.length < 8) {
            return false;
        }
        return (b[0] == (byte) 137 && b[1] == (byte) 80 && b[2] == (byte) 78 && b[3] == (byte) 71
                && b[4] == (byte) 13 && b[5] == (byte) 10 && b[6] == (byte) 26 && b[7] == (byte) 10);
    }

    private static boolean isBMP(byte[] b) {
        if (b.length < 2) {
            return false;
        }
        return (b[0] == 0x42) && (b[1] == 0x4d);
    }
}