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Badge Baker Offline Feature - Refs #7978
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,165 @@ | ||
| <?php | ||
|
|
||
| /** | ||
| * Php library to Bake the PNG Images | ||
| * | ||
| */ | ||
| class PNGImageBaker | ||
| { | ||
| private $_contents; | ||
| private $_size; | ||
| private $_chunks; | ||
|
|
||
| /** | ||
| * Prepares file for handling metadata. | ||
| * Verifies that this file is a valid PNG file. | ||
| * Unpacks file chunks and reads them into an array. | ||
| * | ||
| * @param string $contents File content as a string | ||
| */ | ||
| public function __construct($contents) { | ||
| $this->_contents = $contents; | ||
| $png_signature = pack("C8", 137, 80, 78, 71, 13, 10, 26, 10); | ||
| // Read 8 bytes of PNG header and verify. | ||
| $header = substr($this->_contents, 0, 8); | ||
| if ($header != $png_signature) { | ||
| echo 'This is not a valid PNG image'; | ||
| } | ||
| $this->_size = strlen($this->_contents); | ||
| $this->_chunks = array(); | ||
| // Skip 8 bytes of IHDR image header. | ||
| $position = 8; | ||
| do { | ||
| $chunk = @unpack('Nsize/a4type', substr($this->_contents, $position, 8)); | ||
| $this->_chunks[$chunk['type']][] = substr($this->_contents, $position + 8, $chunk['size']); | ||
| // Skip 12 bytes chunk overhead. | ||
| $position += $chunk['size'] + 12; | ||
| } while ($position < $this->_size); | ||
| } | ||
|
|
||
| /** | ||
| * Checks if a key already exists in the chunk of said type. | ||
| * We need to avoid writing same keyword into file chunks. | ||
| * | ||
| * @param string $type Chunk type, like iTXt, tEXt, etc. | ||
| * @param string $check Keyword that needs to be checked. | ||
| * | ||
| * @return boolean (true|false) True if file is safe to write this keyword, false otherwise. | ||
| */ | ||
| public function checkChunks($type, $check) { | ||
| if (array_key_exists($type, $this->_chunks)) { | ||
| foreach (array_keys($this->_chunks[$type]) as $typekey) { | ||
| list($key, $data) = explode("\0", $this->_chunks[$type][$typekey]); | ||
| if (strcmp($key, $check) == 0) { | ||
| echo 'Key "' . $check . '" already exists in "' . $type . '" chunk.'; | ||
| return false; | ||
| } | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
|
|
||
| /** | ||
| * Add a chunk by type with given key and text | ||
| * | ||
| * @param string $chunkType Chunk type, like iTXt, tEXt, etc. | ||
| * @param string $key Keyword that needs to be added. | ||
| * @param string $value Currently an assertion URL that is added to an image metadata. | ||
| * | ||
| * @return string $result File content with a new chunk as a string. | ||
| */ | ||
| public function addChunk($chunkType, $key, $value) { | ||
|
|
||
| $chunkData = $key . "\0" . $value; | ||
| $crc = pack("N", crc32($chunkType . $chunkData)); | ||
| $len = pack("N", strlen($chunkData)); | ||
|
|
||
| $newChunk = $len . $chunkType . $chunkData . $crc; | ||
| $result = substr($this->_contents, 0, $this->_size - 12) | ||
| . $newChunk | ||
| . substr($this->_contents, $this->_size - 12, 12); | ||
| return $result; | ||
| } | ||
|
|
||
| /** | ||
| * removes a chunk by type with given key and text | ||
| * | ||
| * @param string $chunkType Chunk type, like iTXt, tEXt, etc. | ||
| * @param string $key Keyword that needs to be deleted. | ||
| * @param string $png the png image. | ||
| * | ||
| * @return string $result New File content. | ||
| */ | ||
| public function removeChunks($chunkType, $key, $png) { | ||
| // Read the magic bytes and verify | ||
| $retval = substr($png,0,8); | ||
| $ipos = 8; | ||
| if ($retval != "\x89PNG\x0d\x0a\x1a\x0a") | ||
| throw new Exception('Is not a valid PNG image'); | ||
| // Loop through the chunks. Byte 0-3 is length, Byte 4-7 is type | ||
| $chunkHeader = substr($png,$ipos,8); | ||
| $ipos = $ipos + 8; | ||
| while ($chunkHeader) { | ||
| // Extract length and type from binary data | ||
| $chunk = @unpack('Nsize/a4type', $chunkHeader); | ||
| $skip = false; | ||
| if ( $chunk['type'] == $chunkType ) { | ||
| $data = substr($png,$ipos,$chunk['size']); | ||
| $sections = explode("\0", $data); | ||
| print_r($sections); | ||
| if ( $sections[0] == $key ) $skip = true; | ||
| } | ||
| // Extract the data and the CRC | ||
| $data = substr($png,$ipos,$chunk['size']+4); | ||
| $ipos = $ipos + $chunk['size'] + 4; | ||
| // Add in the header, data, and CRC | ||
| if ( ! $skip ) $retval = $retval . $chunkHeader . $data; | ||
| // Read next chunk header | ||
| $chunkHeader = substr($png,$ipos,8); | ||
| $ipos = $ipos + 8; | ||
| } | ||
| return $retval; | ||
| } | ||
|
|
||
| /** | ||
| * Extracts the baked PNG info by the Key | ||
| * | ||
| * @param string $png the png image | ||
| * @param string $key Keyword that needs to be searched. | ||
| * | ||
| * @return mixed - If there is an error - boolean false is returned | ||
| * If there is PNG information that matches the key an array is returned | ||
| * | ||
| */ | ||
| public function extractBadgeInfo($png, $key='openbadges') { | ||
| // Read the magic bytes and verify | ||
| $retval = substr($png,0,8); | ||
| $ipos = 8; | ||
| if ($retval != "\x89PNG\x0d\x0a\x1a\x0a") { | ||
| return false; | ||
| } | ||
|
|
||
| // Loop through the chunks. Byte 0-3 is length, Byte 4-7 is type | ||
| $chunkHeader = substr($png,$ipos,8); | ||
| $ipos = $ipos + 8; | ||
| while ($chunkHeader) { | ||
| // Extract length and type from binary data | ||
| $chunk = @unpack('Nsize/a4type', $chunkHeader); | ||
| $skip = false; | ||
| if ($chunk['type'] == 'tEXt') { | ||
| $data = substr($png,$ipos,$chunk['size']); | ||
| $sections = explode("\0", $data); | ||
| if ($sections[0] == $key) { | ||
| return $sections; | ||
| } | ||
| } | ||
| // Extract the data and the CRC | ||
| $data = substr($png,$ipos,$chunk['size']+4); | ||
| $ipos = $ipos + $chunk['size'] + 4; | ||
|
|
||
| // Read next chunk header | ||
| $chunkHeader = substr($png,$ipos,8); | ||
| $ipos = $ipos + 8; | ||
| } | ||
| } | ||
| } |
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