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58 lines
1.9 KiB
58 lines
1.9 KiB
/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) Under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for Additional information regarding copyright ownership.
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The ASF licenses this file to You Under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed Under the License is distributed on an "AS Is" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations Under the License.
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==================================================================== */
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namespace Npoi.Core.Util
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{
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public class PngUtils
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{
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/**
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* File header for PNG format.
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*/
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private static byte[] PNG_FILE_HEADER =
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new byte[] { (byte)0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
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private PngUtils()
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{
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// no instances of this class
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}
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/**
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* Checks if the offset matches the PNG header.
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*
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* @param data the data to check.
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* @param offset the offset to check at.
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* @return {@code true} if the offset matches.
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*/
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public static bool MatchesPngHeader(byte[] data, int offset)
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{
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if (data == null || data.Length - offset < PNG_FILE_HEADER.Length)
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{
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return false;
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}
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for (int i = 0; i < PNG_FILE_HEADER.Length; i++)
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{
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if (PNG_FILE_HEADER[i] != data[i + offset])
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{
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return false;
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}
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}
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return true;
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}
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}
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}
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