Yannick Warnier
9 years ago
commit
2208ae4927
@ -0,0 +1,165 @@ |
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<?php |
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|
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/** |
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* Php library to Bake the PNG Images |
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* |
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*/ |
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class PNGImageBaker |
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{ |
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private $_contents; |
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private $_size; |
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private $_chunks; |
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|
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/** |
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* Prepares file for handling metadata. |
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* Verifies that this file is a valid PNG file. |
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* Unpacks file chunks and reads them into an array. |
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* |
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* @param string $contents File content as a string |
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*/ |
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public function __construct($contents) { |
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$this->_contents = $contents; |
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$png_signature = pack("C8", 137, 80, 78, 71, 13, 10, 26, 10); |
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// Read 8 bytes of PNG header and verify. |
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$header = substr($this->_contents, 0, 8); |
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if ($header != $png_signature) { |
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echo 'This is not a valid PNG image'; |
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} |
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$this->_size = strlen($this->_contents); |
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$this->_chunks = array(); |
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// Skip 8 bytes of IHDR image header. |
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$position = 8; |
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do { |
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$chunk = @unpack('Nsize/a4type', substr($this->_contents, $position, 8)); |
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$this->_chunks[$chunk['type']][] = substr($this->_contents, $position + 8, $chunk['size']); |
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// Skip 12 bytes chunk overhead. |
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$position += $chunk['size'] + 12; |
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} while ($position < $this->_size); |
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} |
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|
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/** |
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* Checks if a key already exists in the chunk of said type. |
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* We need to avoid writing same keyword into file chunks. |
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* |
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* @param string $type Chunk type, like iTXt, tEXt, etc. |
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* @param string $check Keyword that needs to be checked. |
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* |
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* @return boolean (true|false) True if file is safe to write this keyword, false otherwise. |
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*/ |
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public function checkChunks($type, $check) { |
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if (array_key_exists($type, $this->_chunks)) { |
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foreach (array_keys($this->_chunks[$type]) as $typekey) { |
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list($key, $data) = explode("\0", $this->_chunks[$type][$typekey]); |
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if (strcmp($key, $check) == 0) { |
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echo 'Key "' . $check . '" already exists in "' . $type . '" chunk.'; |
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return false; |
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} |
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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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* Add a chunk by type with given key and text |
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* |
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* @param string $chunkType Chunk type, like iTXt, tEXt, etc. |
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* @param string $key Keyword that needs to be added. |
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* @param string $value Currently an assertion URL that is added to an image metadata. |
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* |
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* @return string $result File content with a new chunk as a string. |
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*/ |
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public function addChunk($chunkType, $key, $value) { |
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|
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$chunkData = $key . "\0" . $value; |
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$crc = pack("N", crc32($chunkType . $chunkData)); |
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$len = pack("N", strlen($chunkData)); |
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|
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$newChunk = $len . $chunkType . $chunkData . $crc; |
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$result = substr($this->_contents, 0, $this->_size - 12) |
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. $newChunk |
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. substr($this->_contents, $this->_size - 12, 12); |
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return $result; |
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} |
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|
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/** |
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* removes a chunk by type with given key and text |
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* |
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* @param string $chunkType Chunk type, like iTXt, tEXt, etc. |
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* @param string $key Keyword that needs to be deleted. |
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* @param string $png the png image. |
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* |
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* @return string $result New File content. |
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*/ |
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public function removeChunks($chunkType, $key, $png) { |
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// Read the magic bytes and verify |
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$retval = substr($png,0,8); |
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$ipos = 8; |
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if ($retval != "\x89PNG\x0d\x0a\x1a\x0a") |
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throw new Exception('Is not a valid PNG image'); |
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// Loop through the chunks. Byte 0-3 is length, Byte 4-7 is type |
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$chunkHeader = substr($png,$ipos,8); |
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$ipos = $ipos + 8; |
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while ($chunkHeader) { |
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// Extract length and type from binary data |
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$chunk = @unpack('Nsize/a4type', $chunkHeader); |
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$skip = false; |
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if ( $chunk['type'] == $chunkType ) { |
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$data = substr($png,$ipos,$chunk['size']); |
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$sections = explode("\0", $data); |
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print_r($sections); |
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if ( $sections[0] == $key ) $skip = true; |
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} |
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// Extract the data and the CRC |
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$data = substr($png,$ipos,$chunk['size']+4); |
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$ipos = $ipos + $chunk['size'] + 4; |
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// Add in the header, data, and CRC |
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if ( ! $skip ) $retval = $retval . $chunkHeader . $data; |
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// Read next chunk header |
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$chunkHeader = substr($png,$ipos,8); |
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$ipos = $ipos + 8; |
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} |
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return $retval; |
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} |
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|
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/** |
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* Extracts the baked PNG info by the Key |
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* |
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* @param string $png the png image |
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* @param string $key Keyword that needs to be searched. |
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* |
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* @return mixed - If there is an error - boolean false is returned |
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* If there is PNG information that matches the key an array is returned |
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* |
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*/ |
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public function extractBadgeInfo($png, $key='openbadges') { |
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// Read the magic bytes and verify |
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$retval = substr($png,0,8); |
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$ipos = 8; |
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if ($retval != "\x89PNG\x0d\x0a\x1a\x0a") { |
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return false; |
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} |
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|
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// Loop through the chunks. Byte 0-3 is length, Byte 4-7 is type |
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$chunkHeader = substr($png,$ipos,8); |
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$ipos = $ipos + 8; |
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while ($chunkHeader) { |
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// Extract length and type from binary data |
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$chunk = @unpack('Nsize/a4type', $chunkHeader); |
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$skip = false; |
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if ($chunk['type'] == 'tEXt') { |
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$data = substr($png,$ipos,$chunk['size']); |
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$sections = explode("\0", $data); |
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if ($sections[0] == $key) { |
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return $sections; |
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} |
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} |
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// Extract the data and the CRC |
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$data = substr($png,$ipos,$chunk['size']+4); |
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$ipos = $ipos + $chunk['size'] + 4; |
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|
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// Read next chunk header |
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$chunkHeader = substr($png,$ipos,8); |
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$ipos = $ipos + 8; |
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} |
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} |
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} |
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