76 lines
2.4 KiB
PHP
76 lines
2.4 KiB
PHP
<?php
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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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* 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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* This code was originally taken from:
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* https://github.com/ktomk/Miscellaneous/blob/master/get_png_imageinfo/get_png_imageinfo.php
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* It has been modified to fix bugs and improve code formatting
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*
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* Get image-information from PNG file
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*
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* php's getimagesize does not support additional image information
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* from PNG files like channels or bits.
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*
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* get_png_imageinfo() can be used to obtain this information
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* from PNG files.
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*
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* @author Tom Klingenberg <lastflood.net>
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* @license Apache 2.0
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* @link https://github.com/ktomk/Miscellaneous/blob/master/get_png_imageinfo/get_png_imageinfo.php
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* @link http://www.libpng.org/pub/png/spec/iso/index-object.html#11IHDR
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*
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* @param string $file filename
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* @return array|bool image information, FALSE on error
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*/
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function get_png_imageinfo($file) {
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if (! is_file($file)) {
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return false;
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}
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$info = unpack(
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'a8sig/Nchunksize/A4chunktype/Nwidth/Nheight/Cbit-depth/Ccolor/Ccompression/Cfilter/Cinterface',
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file_get_contents($file, 0, null, 0, 29)
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);
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if (empty($info)) {
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return false;
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}
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if ("\x89\x50\x4E\x47\x0D\x0A\x1A\x0A" != array_shift($info)) {
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return false; // no PNG signature
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}
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if (13 != array_shift($info)) {
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return false; // wrong length for IHDR chunk
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}
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if ('IHDR'!==array_shift($info)) {
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return false; // a non-IHDR chunk singals invalid data
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}
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$color = $info['color'];
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$type = array(
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0 => 'Greyscale',
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2 => 'Truecolour',
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3 => 'Indexed-colour',
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4 => 'Greyscale with alpha',
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6 => 'Truecolour with alpha'
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);
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if (empty($type[$color])) {
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return false; // invalid color value
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}
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$info['color-type'] = $type[$color];
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$samples = ((($color % 4) % 3) ? 3 : 1) + ($color > 3 ? 1 : 0);
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$info['channels'] = $samples;
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$info['bits'] = $info['bit-depth'];
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return $info;
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}
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