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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You 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.
==================================================================== */

package org.apache.poi.sl.image;

import java.awt.Dimension;
import java.awt.Rectangle;

import org.apache.poi.util.Internal;
import org.apache.poi.util.Units;

@Internal
public class ImageHeaderPICT {
    /**
     * skip the first 512 bytes - they are MAC specific crap
     */
    public static final int PICT_HEADER_OFFSET = 512;

    public static final double DEFAULT_RESOLUTION = Units.POINT_DPI;

    private static final byte[] V2_HEADER = {
            0x00, 0x11,       // v2 version opcode
            0x02, (byte) 0xFF, // version number of new picture
            0x0C, 0x00,        // header opcode
            (byte) 0xFF, (byte) 0xFE, 0x00, 0x00 // pic size dummy
    };

    private final Rectangle bounds;
    private final double hRes, vRes;

    public ImageHeaderPICT(byte[] data, final int off) {
        // http://mirrors.apple2.org.za/apple.cabi.net/Graphics/PICT.and_QT.INFO/PICT.file.format.TI.txt
        int offset = off;
        // low order 16 bits of picture size - can be ignored
        offset += 2;
        // rectangular bounding box of picture, at 72 dpi
        // rect : 8 bytes (top, left, bottom, right: integer)
        int y1 = readUnsignedShort(data, offset); offset += 2;
        int x1 = readUnsignedShort(data, offset); offset += 2;
        int y2 = readUnsignedShort(data, offset); offset += 2;
        int x2 = readUnsignedShort(data, offset); offset += 2;

        // check for version 2 ... otherwise we don't read any further
        boolean isV2 = true;
        for (byte b : V2_HEADER) {
            if (b != data[offset++]) {
                isV2 = false;
                break;
            }
        }

        if (isV2) {
            // 4 bytes - fixed, horizontal resolution (dpi) of source data
            hRes = readFixedPoint(data, offset); offset += 4;
            // 4 bytes - fixed, vertical resolution (dpi) of source data
            vRes = readFixedPoint(data, offset); offset += 4;
        } else {
            hRes = DEFAULT_RESOLUTION;
            vRes = DEFAULT_RESOLUTION;
        }

        bounds = new Rectangle(x1,y1,x2-x1,y2-y1);
    }

    public Dimension getSize() {
        int height = (int)Math.round(bounds.height*DEFAULT_RESOLUTION/vRes);
        int width = (int)Math.round(bounds.width*DEFAULT_RESOLUTION/hRes);
        return new Dimension(width, height);
    }

    public Rectangle getBounds() {
        return bounds;
    }

    private static int readUnsignedShort(byte[] data, int offset) {
        int b0 = data[offset] & 0xFF;
        int b1 = data[offset+1] & 0xFF;
        return b0 << 8 | b1;
    }

    private static double readFixedPoint(byte[] data, int offset) {
        int b0 = data[offset] & 0xFF;
        int b1 = data[offset+1] & 0xFF;
        int b2 = data[offset+2] & 0xFF;
        int b3 = data[offset+3] & 0xFF;
        int i = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
        return i / (double)0x10000;
    }
}