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83 lines
3.4 KiB
83 lines
3.4 KiB
/****************************************************************************
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Copyright (c) 2021-2023 Xiamen Yaji Software Co., Ltd.
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http://www.cocos.com
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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****************************************************************************/
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// Copyright 2009 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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#include "base/etc1.h"
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#include <string.h>
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static const char kMagic[] = {'P', 'K', 'M', ' ', '1', '0'};
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static const etc1_uint32 ETC1_PKM_FORMAT_OFFSET = 6;
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static const etc1_uint32 ETC1_PKM_ENCODED_WIDTH_OFFSET = 8;
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static const etc1_uint32 ETC1_PKM_ENCODED_HEIGHT_OFFSET = 10;
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static const etc1_uint32 ETC1_PKM_WIDTH_OFFSET = 12;
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static const etc1_uint32 ETC1_PKM_HEIGHT_OFFSET = 14;
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static const etc1_uint32 ETC1_RGB_NO_MIPMAPS = 0;
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static etc1_uint32 readBEUint16(const etc1_byte *pIn) {
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return (pIn[0] << 8) | pIn[1];
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}
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// Check if a PKM header is correctly formatted.
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etc1_bool etc1_pkm_is_valid(const etc1_byte *pHeader) {
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if (memcmp(pHeader, kMagic, sizeof(kMagic))) {
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return false;
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}
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etc1_uint32 format = readBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET);
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etc1_uint32 encodedWidth = readBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET);
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etc1_uint32 encodedHeight = readBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET);
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etc1_uint32 width = readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
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etc1_uint32 height = readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
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return format == ETC1_RGB_NO_MIPMAPS &&
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encodedWidth >= width && encodedWidth - width < 4 &&
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encodedHeight >= height && encodedHeight - height < 4;
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}
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// Read the image width from a PKM header
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etc1_uint32 etc1_pkm_get_width(const etc1_byte *pHeader) {
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return readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
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}
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// Read the image height from a PKM header
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etc1_uint32 etc1_pkm_get_height(const etc1_byte *pHeader) {
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return readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
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}
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