| /* ==================================================================== |
| 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.util; |
| |
| |
| public final class PngUtils { |
| |
| /** |
| * File header for PNG format. |
| */ |
| private static final byte[] PNG_FILE_HEADER = |
| new byte[] { (byte) 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }; |
| |
| private PngUtils() { |
| // no instances of this class |
| } |
| |
| /** |
| * Checks if the offset matches the PNG header. |
| * |
| * @param data the data to check. |
| * @param offset the offset to check at. |
| * @return {@code true} if the offset matches. |
| */ |
| public static boolean matchesPngHeader(byte[] data, int offset) { |
| if (data == null || data.length - offset < PNG_FILE_HEADER.length) { |
| return false; |
| } |
| |
| for (int i = 0; i < PNG_FILE_HEADER.length; i++) { |
| if (PNG_FILE_HEADER[i] != data[i + offset]) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| } |