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Diffstat (limited to 'modules/getid3/module.graphic.png.php')
| -rw-r--r-- | modules/getid3/module.graphic.png.php | 556 |
1 files changed, 556 insertions, 0 deletions
diff --git a/modules/getid3/module.graphic.png.php b/modules/getid3/module.graphic.png.php new file mode 100644 index 00000000..daa39221 --- /dev/null +++ b/modules/getid3/module.graphic.png.php @@ -0,0 +1,556 @@ +<?php +// +----------------------------------------------------------------------+ +// | PHP version 5 | +// +----------------------------------------------------------------------+ +// | Copyright (c) 2002-2006 James Heinrich, Allan Hansen | +// +----------------------------------------------------------------------+ +// | This source file is subject to version 2 of the GPL license, | +// | that is bundled with this package in the file license.txt and is | +// | available through the world-wide-web at the following url: | +// | http://www.gnu.org/copyleft/gpl.html | +// +----------------------------------------------------------------------+ +// | getID3() - http://getid3.sourceforge.net or http://www.getid3.org | +// +----------------------------------------------------------------------+ +// | Authors: James Heinrich <infoØgetid3*org> | +// | Allan Hansen <ahØartemis*dk> | +// +----------------------------------------------------------------------+ +// | module.graphic.png.php | +// | Module for analyzing PNG graphic files. | +// | dependencies: zlib support in PHP (optional) | +// +----------------------------------------------------------------------+ +// +// $Id: module.graphic.png.php,v 1.4 2006/11/02 10:48:02 ah Exp $ + + + +class getid3_png extends getid3_handler +{ + + public function Analyze() { + + $getid3 = $this->getid3; + + $getid3->info['png'] = array (); + $info_png = &$getid3->info['png']; + + $getid3->info['fileformat'] = 'png'; + $getid3->info['video']['dataformat'] = 'png'; + $getid3->info['video']['lossless'] = false; + + fseek($getid3->fp, $getid3->info['avdataoffset'], SEEK_SET); + $png_filedata = fread($getid3->fp, getid3::FREAD_BUFFER_SIZE); + + // Magic bytes "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A" + + $offset = 8; + + while (((ftell($getid3->fp) - (strlen($png_filedata) - $offset)) < $getid3->info['filesize'])) { + + $chunk['data_length'] = getid3_lib::BigEndian2Int(substr($png_filedata, $offset, 4)); + $offset += 4; + while (((strlen($png_filedata) - $offset) < ($chunk['data_length'] + 4)) && (ftell($getid3->fp) < $getid3->info['filesize'])) { + $png_filedata .= fread($getid3->fp, getid3::FREAD_BUFFER_SIZE); + } + + $chunk['type_text'] = substr($png_filedata, $offset, 4); + $chunk['type_raw'] = getid3_lib::BigEndian2Int($chunk['type_text']); + $offset += 4; + + $chunk['data'] = substr($png_filedata, $offset, $chunk['data_length']); + $offset += $chunk['data_length']; + + $chunk['crc'] = getid3_lib::BigEndian2Int(substr($png_filedata, $offset, 4)); + $offset += 4; + + $chunk['flags']['ancilliary'] = (bool)($chunk['type_raw'] & 0x20000000); + $chunk['flags']['private'] = (bool)($chunk['type_raw'] & 0x00200000); + $chunk['flags']['reserved'] = (bool)($chunk['type_raw'] & 0x00002000); + $chunk['flags']['safe_to_copy'] = (bool)($chunk['type_raw'] & 0x00000020); + + // shortcut + $info_png[$chunk['type_text']] = array (); + $info_png_chunk_type_text = &$info_png[$chunk['type_text']]; + + switch ($chunk['type_text']) { + + case 'IHDR': // Image Header + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['width'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 4)); + $info_png_chunk_type_text['height'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 4)); + + getid3_lib::ReadSequence('BigEndian2Int', $info_png_chunk_type_text['raw'], $chunk['data'], 8, + array ( + 'bit_depth' => 1, + 'color_type' => 1, + 'compression_method' => 1, + 'filter_method' => 1, + 'interlace_method' => 1 + ) + ); + + $info_png_chunk_type_text['compression_method_text'] = getid3_png::PNGcompressionMethodLookup($info_png_chunk_type_text['raw']['compression_method']); + $info_png_chunk_type_text['color_type']['palette'] = (bool)($info_png_chunk_type_text['raw']['color_type'] & 0x01); + $info_png_chunk_type_text['color_type']['true_color'] = (bool)($info_png_chunk_type_text['raw']['color_type'] & 0x02); + $info_png_chunk_type_text['color_type']['alpha'] = (bool)($info_png_chunk_type_text['raw']['color_type'] & 0x04); + + $getid3->info['video']['resolution_x'] = $info_png_chunk_type_text['width']; + $getid3->info['video']['resolution_y'] = $info_png_chunk_type_text['height']; + + $getid3->info['video']['bits_per_sample'] = getid3_png::IHDRcalculateBitsPerSample($info_png_chunk_type_text['raw']['color_type'], $info_png_chunk_type_text['raw']['bit_depth']); + break; + + + case 'PLTE': // Palette + $info_png_chunk_type_text['header'] = $chunk; + $palette_offset = 0; + for ($i = 0; $i <= 255; $i++) { + $red = @getid3_lib::BigEndian2Int($chunk['data']{$palette_offset++}); + $green = @getid3_lib::BigEndian2Int($chunk['data']{$palette_offset++}); + $blue = @getid3_lib::BigEndian2Int($chunk['data']{$palette_offset++}); + $info_png_chunk_type_text[$i] = (($red << 16) | ($green << 8) | ($blue)); + } + break; + + + case 'tRNS': // Transparency + $info_png_chunk_type_text['header'] = $chunk; + switch ($info_png['IHDR']['raw']['color_type']) { + case 0: + $info_png_chunk_type_text['transparent_color_gray'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 2)); + break; + + case 2: + $info_png_chunk_type_text['transparent_color_red'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 2)); + $info_png_chunk_type_text['transparent_color_green'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 2, 2)); + $info_png_chunk_type_text['transparent_color_blue'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 2)); + break; + + case 3: + for ($i = 0; $i < strlen($chunk['data']); $i++) { + $info_png_chunk_type_text['palette_opacity'][$i] = getid3_lib::BigEndian2Int($chunk['data'][$i]); + } + break; + + case 4: + case 6: + throw new getid3_exception('Invalid color_type in tRNS chunk: '.$info_png['IHDR']['raw']['color_type']); + + default: + $getid3->warning('Unhandled color_type in tRNS chunk: '.$info_png['IHDR']['raw']['color_type']); + break; + } + break; + + + case 'gAMA': // Image Gamma + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['gamma'] = getid3_lib::BigEndian2Int($chunk['data']) / 100000; + break; + + + case 'cHRM': // Primary Chromaticities + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['white_x'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 4)) / 100000; + $info_png_chunk_type_text['white_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 4)) / 100000; + $info_png_chunk_type_text['red_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 8, 4)) / 100000; + $info_png_chunk_type_text['red_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 12, 4)) / 100000; + $info_png_chunk_type_text['green_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 16, 4)) / 100000; + $info_png_chunk_type_text['green_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 20, 4)) / 100000; + $info_png_chunk_type_text['blue_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 24, 4)) / 100000; + $info_png_chunk_type_text['blue_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 28, 4)) / 100000; + break; + + + case 'sRGB': // Standard RGB Color Space + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['reindering_intent'] = getid3_lib::BigEndian2Int($chunk['data']); + $info_png_chunk_type_text['reindering_intent_text'] = getid3_png::PNGsRGBintentLookup($info_png_chunk_type_text['reindering_intent']); + break; + + + case 'iCCP': // Embedded ICC Profile + $info_png_chunk_type_text['header'] = $chunk; + list($profilename, $compressiondata) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['profile_name'] = $profilename; + $info_png_chunk_type_text['compression_method'] = getid3_lib::BigEndian2Int($compressiondata[0]); + $info_png_chunk_type_text['compression_profile'] = substr($compressiondata, 1); + $info_png_chunk_type_text['compression_method_text'] = getid3_png::PNGcompressionMethodLookup($info_png_chunk_type_text['compression_method']); + break; + + + case 'tEXt': // Textual Data + $info_png_chunk_type_text['header'] = $chunk; + list($keyword, $text) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['keyword'] = $keyword; + $info_png_chunk_type_text['text'] = $text; + + $info_png['comments'][$info_png_chunk_type_text['keyword']][] = $info_png_chunk_type_text['text']; + break; + + + case 'zTXt': // Compressed Textual Data + $info_png_chunk_type_text['header'] = $chunk; + list($keyword, $otherdata) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['keyword'] = $keyword; + $info_png_chunk_type_text['compression_method'] = getid3_lib::BigEndian2Int(substr($otherdata, 0, 1)); + $info_png_chunk_type_text['compressed_text'] = substr($otherdata, 1); + $info_png_chunk_type_text['compression_method_text'] = getid3_png::PNGcompressionMethodLookup($info_png_chunk_type_text['compression_method']); + + if ($info_png_chunk_type_text['compression_method'] != 0) { + // unknown compression method + break; + } + + if (function_exists('gzuncompress')) { + $info_png_chunk_type_text['text'] = gzuncompress($info_png_chunk_type_text['compressed_text']); + } + else { + if (!@$this->zlib_warning) { + $getid3->warning('PHP does not have --with-zlib support - cannot gzuncompress()'); + } + $this->zlib_warning = true; + } + + + if (isset($info_png_chunk_type_text['text'])) { + $info_png['comments'][$info_png_chunk_type_text['keyword']][] = $info_png_chunk_type_text['text']; + } + break; + + + case 'iTXt': // International Textual Data + $info_png_chunk_type_text['header'] = $chunk; + list($keyword, $otherdata) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['keyword'] = $keyword; + $info_png_chunk_type_text['compression'] = (bool)getid3_lib::BigEndian2Int(substr($otherdata, 0, 1)); + $info_png_chunk_type_text['compression_method'] = getid3_lib::BigEndian2Int($otherdata[1]); + $info_png_chunk_type_text['compression_method_text'] = getid3_png::PNGcompressionMethodLookup($info_png_chunk_type_text['compression_method']); + list($languagetag, $translatedkeyword, $text) = explode("\x00", substr($otherdata, 2), 3); + $info_png_chunk_type_text['language_tag'] = $languagetag; + $info_png_chunk_type_text['translated_keyword'] = $translatedkeyword; + + if ($info_png_chunk_type_text['compression']) { + + switch ($info_png_chunk_type_text['compression_method']) { + case 0: + if (function_exists('gzuncompress')) { + $info_png_chunk_type_text['text'] = gzuncompress($text); + } + else { + if (!@$this->zlib_warning) { + $getid3->warning('PHP does not have --with-zlib support - cannot gzuncompress()'); + } + $this->zlib_warning = true; + } + break; + + default: + // unknown compression method + break; + } + + } else { + + $info_png_chunk_type_text['text'] = $text; + + } + + if (isset($info_png_chunk_type_text['text'])) { + $info_png['comments'][$info_png_chunk_type_text['keyword']][] = $info_png_chunk_type_text['text']; + } + break; + + + case 'bKGD': // Background Color + $info_png_chunk_type_text['header'] = $chunk; + switch ($info_png['IHDR']['raw']['color_type']) { + case 0: + case 4: + $info_png_chunk_type_text['background_gray'] = getid3_lib::BigEndian2Int($chunk['data']); + break; + + case 2: + case 6: + $info_png_chunk_type_text['background_red'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0 * $info_png['IHDR']['raw']['bit_depth'], $info_png['IHDR']['raw']['bit_depth'])); + $info_png_chunk_type_text['background_green'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 1 * $info_png['IHDR']['raw']['bit_depth'], $info_png['IHDR']['raw']['bit_depth'])); + $info_png_chunk_type_text['background_blue'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 2 * $info_png['IHDR']['raw']['bit_depth'], $info_png['IHDR']['raw']['bit_depth'])); + break; + + case 3: + $info_png_chunk_type_text['background_index'] = getid3_lib::BigEndian2Int($chunk['data']); + break; + + default: + break; + } + break; + + + case 'pHYs': // Physical Pixel Dimensions + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['pixels_per_unit_x'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 4)); + $info_png_chunk_type_text['pixels_per_unit_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 4)); + $info_png_chunk_type_text['unit_specifier'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 8, 1)); + $info_png_chunk_type_text['unit'] = getid3_png::PNGpHYsUnitLookup($info_png_chunk_type_text['unit_specifier']); + break; + + + case 'sBIT': // Significant Bits + $info_png_chunk_type_text['header'] = $chunk; + switch ($info_png['IHDR']['raw']['color_type']) { + case 0: + $info_png_chunk_type_text['significant_bits_gray'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 1)); + break; + + case 2: + case 3: + $info_png_chunk_type_text['significant_bits_red'] = getid3_lib::BigEndian2Int($chunk['data'][0]); + $info_png_chunk_type_text['significant_bits_green'] = getid3_lib::BigEndian2Int($chunk['data'][1]); + $info_png_chunk_type_text['significant_bits_blue'] = getid3_lib::BigEndian2Int($chunk['data'][2]); + break; + + case 4: + $info_png_chunk_type_text['significant_bits_gray'] = getid3_lib::BigEndian2Int($chunk['data'][0]); + $info_png_chunk_type_text['significant_bits_alpha'] = getid3_lib::BigEndian2Int($chunk['data'][1]); + break; + + case 6: + $info_png_chunk_type_text['significant_bits_red'] = getid3_lib::BigEndian2Int($chunk['data'][0]); + $info_png_chunk_type_text['significant_bits_green'] = getid3_lib::BigEndian2Int($chunk['data'][1]); + $info_png_chunk_type_text['significant_bits_blue'] = getid3_lib::BigEndian2Int($chunk['data'][2]); + $info_png_chunk_type_text['significant_bits_alpha'] = getid3_lib::BigEndian2Int($chunk['data'][3]); + break; + + default: + break; + } + break; + + + case 'sPLT': // Suggested Palette + $info_png_chunk_type_text['header'] = $chunk; + + list($palettename, $otherdata) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['palette_name'] = $palettename; + + $info_png_chunk_type_text['sample_depth_bits'] = getid3_lib::BigEndian2Int($otherdata[0]); + $info_png_chunk_type_text['sample_depth_bytes'] = $info_png_chunk_type_text['sample_depth_bits'] / 8; + + $s_plt_offset = 1; + $paletteCounter = 0; + while ($s_plt_offset < strlen($otherdata)) { + + $info_png_chunk_type_text['red'][$paletteCounter] = getid3_lib::BigEndian2Int(substr($otherdata, $s_plt_offset, $info_png_chunk_type_text['sample_depth_bytes'])); + $s_plt_offset += $info_png_chunk_type_text['sample_depth_bytes']; + + $info_png_chunk_type_text['green'][$paletteCounter] = getid3_lib::BigEndian2Int(substr($otherdata, $s_plt_offset, $info_png_chunk_type_text['sample_depth_bytes'])); + $s_plt_offset += $info_png_chunk_type_text['sample_depth_bytes']; + + $info_png_chunk_type_text['blue'][$paletteCounter] = getid3_lib::BigEndian2Int(substr($otherdata, $s_plt_offset, $info_png_chunk_type_text['sample_depth_bytes'])); + $s_plt_offset += $info_png_chunk_type_text['sample_depth_bytes']; + + $info_png_chunk_type_text['alpha'][$paletteCounter] = getid3_lib::BigEndian2Int(substr($otherdata, $s_plt_offset, $info_png_chunk_type_text['sample_depth_bytes'])); + $s_plt_offset += $info_png_chunk_type_text['sample_depth_bytes']; + + $info_png_chunk_type_text['frequency'][$paletteCounter] = getid3_lib::BigEndian2Int(substr($otherdata, $s_plt_offset, 2)); + $s_plt_offset += 2; + + $paletteCounter++; + } + break; + + + case 'hIST': // Palette Histogram + $info_png_chunk_type_text['header'] = $chunk; + $h_ist_counter = 0; + while ($h_ist_counter < strlen($chunk['data'])) { + $info_png_chunk_type_text[$h_ist_counter] = getid3_lib::BigEndian2Int(substr($chunk['data'], $h_ist_counter / 2, 2)); + $h_ist_counter += 2; + } + break; + + + case 'tIME': // Image Last-Modification Time + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['year'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 2)); + $info_png_chunk_type_text['month'] = getid3_lib::BigEndian2Int($chunk['data']{2}); + $info_png_chunk_type_text['day'] = getid3_lib::BigEndian2Int($chunk['data']{3}); + $info_png_chunk_type_text['hour'] = getid3_lib::BigEndian2Int($chunk['data']{4}); + $info_png_chunk_type_text['minute'] = getid3_lib::BigEndian2Int($chunk['data']{5}); + $info_png_chunk_type_text['second'] = getid3_lib::BigEndian2Int($chunk['data']{6}); + $info_png_chunk_type_text['unix'] = gmmktime($info_png_chunk_type_text['hour'], $info_png_chunk_type_text['minute'], $info_png_chunk_type_text['second'], $info_png_chunk_type_text['month'], $info_png_chunk_type_text['day'], $info_png_chunk_type_text['year']); + break; + + + case 'oFFs': // Image Offset + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['position_x'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 4), false, true); + $info_png_chunk_type_text['position_y'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 4), false, true); + $info_png_chunk_type_text['unit_specifier'] = getid3_lib::BigEndian2Int($chunk['data'][8]); + $info_png_chunk_type_text['unit'] = getid3_png::PNGoFFsUnitLookup($info_png_chunk_type_text['unit_specifier']); + break; + + + case 'pCAL': // Calibration Of Pixel Values + $info_png_chunk_type_text['header'] = $chunk; + list($calibrationname, $otherdata) = explode("\x00", $chunk['data'], 2); + $info_png_chunk_type_text['calibration_name'] = $calibrationname; + $info_png_chunk_type_text['original_zero'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 4), false, true); + $info_png_chunk_type_text['original_max'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 4, 4), false, true); + $info_png_chunk_type_text['equation_type'] = getid3_lib::BigEndian2Int($chunk['data'][8]); + $info_png_chunk_type_text['equation_type_text'] = getid3_png::PNGpCALequationTypeLookup($info_png_chunk_type_text['equation_type']); + $info_png_chunk_type_text['parameter_count'] = getid3_lib::BigEndian2Int($chunk['data'][9]); + $info_png_chunk_type_text['parameters'] = explode("\x00", substr($chunk['data'], 10)); + break; + + + case 'sCAL': // Physical Scale Of Image Subject + $info_png_chunk_type_text['header'] = $chunk; + $info_png_chunk_type_text['unit_specifier'] = getid3_lib::BigEndian2Int(substr($chunk['data'], 0, 1)); + $info_png_chunk_type_text['unit'] = getid3_png::PNGsCALUnitLookup($info_png_chunk_type_text['unit_specifier']); + list($info_png_chunk_type_text['pixel_width'], $info_png_chunk_type_text['pixel_height']) = explode("\x00", substr($chunk['data'], 1)); + break; + + + case 'gIFg': // GIF Graphic Control Extension + $gIFg_counter = 0; + if (isset($info_png_chunk_type_text) && is_array($info_png_chunk_type_text)) { + $gIFg_counter = count($info_png_chunk_type_text); + } + $info_png_chunk_type_text[$gIFg_counter]['header'] = $chunk; + $info_png_chunk_type_text[$gIFg_counter]['disposal_method'] = getid3_lib::BigEndian2Int($chunk['data'][0]); + $info_png_chunk_type_text[$gIFg_counter]['user_input_flag'] = getid3_lib::BigEndian2Int($chunk['data'][1]); + $info_png_chunk_type_text[$gIFg_counter]['delay_time'] = getid3_lib::BigEndian2Int($chunk['data'][2]); + break; + + + case 'gIFx': // GIF Application Extension + $gIFx_counter = 0; + if (isset($info_png_chunk_type_text) && is_array($info_png_chunk_type_text)) { + $gIFx_counter = count($info_png_chunk_type_text); + } + $info_png_chunk_type_text[$gIFx_counter]['header'] = $chunk; + $info_png_chunk_type_text[$gIFx_counter]['application_identifier'] = substr($chunk['data'], 0, 8); + $info_png_chunk_type_text[$gIFx_counter]['authentication_code'] = substr($chunk['data'], 8, 3); + $info_png_chunk_type_text[$gIFx_counter]['application_data'] = substr($chunk['data'], 11); + break; + + + case 'IDAT': // Image Data + $idat_information_field_index = 0; + if (isset($info_png['IDAT']) && is_array($info_png['IDAT'])) { + $idat_information_field_index = count($info_png['IDAT']); + } + unset($chunk['data']); + $info_png_chunk_type_text[$idat_information_field_index]['header'] = $chunk; + break; + + + case 'IEND': // Image Trailer + $info_png_chunk_type_text['header'] = $chunk; + break; + + + default: + $info_png_chunk_type_text['header'] = $chunk; + $getid3->warning('Unhandled chunk type: '.$chunk['type_text']); + break; + } + } + + return true; + } + + + + public static function PNGsRGBintentLookup($sRGB) { + + static $lookup = array ( + 0 => 'Perceptual', + 1 => 'Relative colorimetric', + 2 => 'Saturation', + 3 => 'Absolute colorimetric' + ); + return (isset($lookup[$sRGB]) ? $lookup[$sRGB] : 'invalid'); + } + + + + public static function PNGcompressionMethodLookup($compression_method) { + + return ($compression_method == 0 ? 'deflate/inflate' : 'invalid'); + } + + + + public static function PNGpHYsUnitLookup($unit_id) { + + static $lookup = array ( + 0 => 'unknown', + 1 => 'meter' + ); + return (isset($lookup[$unit_id]) ? $lookup[$unit_id] : 'invalid'); + } + + + + public static function PNGoFFsUnitLookup($unit_id) { + + static $lookup = array ( + 0 => 'pixel', + 1 => 'micrometer' + ); + return (isset($lookup[$unit_id]) ? $lookup[$unit_id] : 'invalid'); + } + + + + public static function PNGpCALequationTypeLookup($equation_type) { + + static $lookup = array ( + 0 => 'Linear mapping', + 1 => 'Base-e exponential mapping', + 2 => 'Arbitrary-base exponential mapping', + 3 => 'Hyperbolic mapping' + ); + return (isset($lookup[$equation_type]) ? $lookup[$equation_type] : 'invalid'); + } + + + + public static function PNGsCALUnitLookup($unit_id) { + + static $lookup = array ( + 0 => 'meter', + 1 => 'radian' + ); + return (isset($lookup[$unit_id]) ? $lookup[$unit_id] : 'invalid'); + } + + + + public static function IHDRcalculateBitsPerSample($color_type, $bit_depth) { + + switch ($color_type) { + case 0: // Each pixel is a grayscale sample. + return $bit_depth; + + case 2: // Each pixel is an R,G,B triple + return 3 * $bit_depth; + + case 3: // Each pixel is a palette index; a PLTE chunk must appear. + return $bit_depth; + + case 4: // Each pixel is a grayscale sample, followed by an alpha sample. + return 2 * $bit_depth; + + case 6: // Each pixel is an R,G,B triple, followed by an alpha sample. + return 4 * $bit_depth; + } + return false; + } + +} + + +?>
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