com.googlecode.blaisemath.util.Images Maven / Gradle / Ivy

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package com.googlecode.blaisemath.util;

/*
 * #%L
 * blaise-svg
 * --
 * Copyright (C) 2014 - 2017 Elisha Peterson
 * --
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */


import static com.google.common.base.Preconditions.checkArgument;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Base64;
import java.util.List;
import javax.imageio.ImageIO;

/**
 * Utilities for working with images.
 * 
 * @author elisha
 */
public class Images {
    
    public static final String DATA_URI_PREFIX = "data:";
    private static final String BASE_64_TOKEN = ";base64";
    
    public static final String BMP = "bmp";
    public static final String GIF = "gif";
    public static final String JPEG = "jpeg";
    public static final String JPG = "jpg";
    public static final String PNG = "png";
    
    private static final List IMAGE_FORMATS = Arrays.asList(JPG, JPEG, BMP, GIF, PNG);
    
    /**
     * Encode the target image as standard base-64, with the target format.
     * The result conforms to RFC-4648, and does not include line breaks.
     * 
     * @param image the image to encode
     * @param format the image format (gif, png, bmp, jpg, jpeg)
     * @return base-64 string
     * @throws java.io.IOException
     * 
     * @see Base64
     */
    public static String encodeStandardBase64(BufferedImage image, String format) throws IOException {
        checkArgument(IMAGE_FORMATS.contains(format.toLowerCase()), "Unsupported format: "+format);
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        ImageIO.write(image, format.toLowerCase(), Base64.getEncoder().wrap(os));
        return os.toString();
    }
    
    /**
     * Create an image from a base-64 string.
     * @param base64 input string
     * @return image
     * @throws java.io.IOException if there's a problem reading from the string
     */
    public static BufferedImage decodeStandardBase64(String base64) throws IOException {
        byte[] bytes = Base64.getDecoder().decode(base64);
        InputStream is = new ByteArrayInputStream(bytes);
        return ImageIO.read(is);
    }

    /**
     * Encode the target image as standard base-64, with the target format,
     * and return the result as a data URI.
     * The result conforms to RFC-4648, and does not include line breaks.
     * 
     * @param image the image to encode
     * @param format the image format (gif, png, bmp, jpg, jpeg)
     * @return base-64 string inside an image data URI
     * @throws java.io.IOException if there's a problem encoding
     * 
     * @see Base64
     */
    public static String encodeDataUriBase64(BufferedImage image, String format) throws IOException {
        return DATA_URI_PREFIX + mimeType(format) + BASE_64_TOKEN + ','
                + encodeStandardBase64(image, format);
    }

    /**
     * Create an image from a standard base-64 data URI.
     * @param base64 base-64 string inside an image data URI
     * @return image
     * @throws java.io.IOException if there's a problem reading from the string
     */
    public static BufferedImage decodeDataUriBase64(String base64) throws IOException {
        checkArgument(base64.startsWith(DATA_URI_PREFIX), "Invalid data URI: "+base64);
        int pos = base64.indexOf(',');
        String content = base64.substring(pos+1);
        return decodeStandardBase64(content);
    }
    
    private static String mimeType(String format) {
        String fixedFormat = JPG.equals(format.toLowerCase()) ? JPEG : format.toLowerCase();
        return "image/"+fixedFormat;
    }
    
}