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task: Added list steps as comments to each method via github copilot
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@joserick
joserick committed Mar 13, 2023
1 parent baf7e71 commit 717b066
Showing 1 changed file with 80 additions and 0 deletions.
80 changes: 80 additions & 0 deletions src/PNGMetadata.php
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Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,7 @@ private function extractNodesXML($node)
$child = $node->childNodes->item($i);
if ($child !== null) {
$childValues = $this->extractNodesXML($child);
// if the node has a tag name, it is not a text node
if (isset($child->tagName)) {
[$prefixTagName, $suffixTagName] = explode(':', $child->tagName);
if (is_array($childValues)) {
Expand All @@ -273,6 +274,8 @@ private function extractNodesXML($node)
} else {
$output = $this->arrayMerge($output, $childValues);
}
// if the node has a prefix and the prefix is in the list of prefixes, it is a XMP tag
// if the node has a suffix and the suffix is in the list of suffixes, it is a XMP tag
} elseif (
\in_array($prefixTagName, $this->prefSuffXMP, true)
|| \in_array($prefixTagName, $this->tagsXMP, true)
Expand All @@ -282,9 +285,11 @@ private function extractNodesXML($node)
} else {
$output[$suffixTagName][] = $childValues;
}
// if the node has a prefix and the prefix is not in the list of prefixes, it is not a XMP tag
} else {
$output[$prefixTagName][$suffixTagName][] = $childValues;
}
// if the node does not have a tag name, it is a text node
} elseif ($childValues || $childValues === '0') {
$output = is_array($childValues)
? implode(', ', $childValues)
Expand Down Expand Up @@ -317,22 +322,32 @@ private function extractNodesXML($node)
*/
private function printVertical(string $lastKey = '', ?array $array = null): array
{
// Create a new array to store the result.
$columns = [];

// If the key is not empty, add a colon to the end of the key.
if ($lastKey !== '') {
$lastKey .= ':';
}

// Traverse the array.
foreach ($array ?: $this->metadata as $key => $value) {
// If the value is a array, call the function recursively.
if (is_array($value)) {
// If the value is an indexed array, merge the key and value together.
if (isset($value[0])) {
$columns[] = [$lastKey . $key => implode(',', $value)];
} else {
// If the value is a associative array, call the function recursively.
$columns[] = $this->printVertical($lastKey . $key, $value);
}
} else {
// If the value is not an array, merge the key and value together.
$columns[] = [$lastKey . $key => $value];
}
}

// Return the merged result.
return array_merge(...$columns);
}

Expand All @@ -346,18 +361,26 @@ private function printVertical(string $lastKey = '', ?array $array = null): arra
*/
private function extractChunks(): void
{
// Open the image file in binary mode.
$content = fopen($this->path, 'rb');

// Verify that the file is a PNG file.
if (fread($content, 8) !== "\x89PNG\x0d\x0a\x1a\x0a") {
throw new \InvalidArgumentException('Invalid PNG file signature, path "' . $this->path . '" given.', 104);
}

// The PNG image is composed of a series of chunks. Each chunk is composed of
// a 4-byte length, a 4-byte type, a variable number of data bytes, and a
// 4-byte CRC.
$chunkHeader = fread($content, 8);
while ($chunkHeader) {
$chunk = unpack('Nsize/a4type', $chunkHeader);
if ($chunk['type'] === 'IEND') {
break;
}
// Read the chunk data.
if ($chunk['type'] === 'tEXt') {
// For the tEXt chunk, the data is a keyword and a text string.
$this->chunks[$chunk['type']][] = explode("\0", fread($content, $chunk['size']));
fseek($content, 4, SEEK_CUR);
} else {
Expand All @@ -367,10 +390,13 @@ private function extractChunks(): void
|| $chunk['type'] === 'iTXt'
|| $chunk['type'] === 'bKGD'
) {
// For the eXIf, sRGB, iTXt, and bKGD chunks, the data is a byte
// sequence.
$lastOffset = ftell($content);
$this->chunks[$chunk['type']] = fread($content, $chunk['size']);
fseek($content, $lastOffset, SEEK_SET);
} elseif ($chunk['type'] === 'IHDR') {
// For the IHDR chunk, the data is a series of fields.
$lastOffset = ftell($content);
for ($i = 0; $i < 6; $i++) {
$this->chunks[$chunk['type']][] = fread($content, ($i > 1 ? 1 : 4));
Expand All @@ -394,6 +420,7 @@ private function extractChunks(): void
private function extractIHDR(): void
{
if (isset($this->chunks['IHDR'])) {
// Create a array that will be used to associate the chunk data with the corresponding metadata name.
$ihdr = [
'ImageWidth',
'ImageHeight',
Expand All @@ -418,14 +445,20 @@ private function extractIHDR(): void
],
];

// Loop through each chunk data.
foreach ($this->chunks['IHDR'] as $key => $value) {
// Check if the current chunk data is not the first two bytes of the chunk.
if ($key > 1) {
// Check if the current chunk data is the third byte of the chunk.
if ($key === 2) {
// Add the metadata name (in the $ihdr array) corresponding to the chunk data and the value of the chunk data.
$this->metadata['IHDR'][$ihdr[$key]] = ord($value);
} else {
// Add the metadata name (in the $ihdr array) corresponding to the chunk data and the value of the chunk data.
$this->metadata['IHDR'][$ihdr[$key][8]] = $ihdr[$key][ord($value)];
}
} else {
// Add the metadata name (in the $ihdr array) corresponding to the chunk data and the value of the chunk data.
$this->metadata['IHDR'][$ihdr[$key]] = unpack('Ni', $value)['i'];
}
}
Expand All @@ -436,12 +469,19 @@ private function extractIHDR(): void
/**
* Extract KGD type from bKGD chunk as a array.
*
* The format of bKGD chunk is:
* - For indexed-color images: 1 byte.
* - For grayscale images: 2 bytes.
* - For truecolor images: 6 bytes.
*
* @see PNGMetadata::$metadata For the property whose metadata are storage.
* @see PNGMetadata::$chunks For the property whose chunks data are storage.
*/
private function extractBKGD(): void
{
if (isset($this->chunks['bKGD'])) {
// If the length of bKGD chunk is less than 2, it is an indexed-color images.
// Otherwise it is a grayscale or truecolor images.
$this->metadata['bKGD'] = implode(' ', unpack(strlen($this->chunks['bKGD']) < 2 ? 'C' : 'n*', $this->chunks['bKGD']));
}
}
Expand All @@ -456,8 +496,11 @@ private function extractBKGD(): void
private function extractRGB(): void
{
if (isset($this->chunks['sRGB'])) {
// $rgb is an array with 4 possible values
$rgb = ['Perceptual', 'Relative Colorimetric', 'Saturation', 'Absolute Colorimetric'];
// Unpack the sRGB chunk data as a byte
$unpacked = unpack('C', $this->chunks['sRGB']);
// Set the sRGB value to the value of $rgb that matches the byte
$this->metadata['sRGB'] = $rgb[end($unpacked)] ?? 'Unknown';
}
}
Expand All @@ -471,16 +514,22 @@ private function extractRGB(): void
*/
private function extractExif(): void
{
// Check if eXIf chunk exists.
if (isset($this->chunks['eXIf'])) {
// Open eXIf chunk data as a memory stream.
$this->exif_data = fopen('php://memory', 'r+b');
// Write eXIf chunk data to the memory stream.
fwrite($this->exif_data, $this->chunks['eXIf']);
// Set the pointer of memory stream to the beginning of the stream.
rewind($this->exif_data);

// Read Exif data from memory stream.
$this->metadata['exif'] = array_replace(
$this->metadata['exif'] ?? [],
exif_read_data($this->exif_data, null, true),
);

// Set the pointer of memory stream to the beginning of the stream.
rewind($this->exif_data);
}
}
Expand All @@ -494,12 +543,21 @@ private function extractExif(): void
*/
private function extractTExif(): void
{
// Check if the tEXt chunk is present in the PNG file.
if (isset($this->chunks['tEXt']) && is_array($this->chunks['tEXt'])) {

// Loop over all tEXt chunks.
foreach ($this->chunks['tEXt'] as $exif) {

// Split the key into parts.
[$group, $tag, $tag2] = array_pad(explode(':', $exif[0]), 3, null);

// Convert the thumbnail key to uppercase.
if ($tag === 'thumbnail') {
$tag = strtoupper($tag);
}

// Store the value in the metadata array.
$this->metadata[$group][$tag] = ($tag2 ? [$tag2 => $exif[1]] : $exif[1]);
}
}
Expand All @@ -516,18 +574,27 @@ private function extractTExif(): void
private function extractXMP(): void
{
if (isset($this->chunks['iTXt']) && strncmp($this->chunks['iTXt'], 'XML:com.adobe.xmp', 17) === 0) {
// create a new DOMDocument instance
$dom = new \DOMDocument('1.0', 'UTF-8');
// set the preserveWhiteSpace property to false to remove white space
$dom->preserveWhiteSpace = false;
// set the formatOutput property to false to remove extra line breaks
$dom->formatOutput = false;
// set the substituteEntities property to false to prevent entity substitution
$dom->substituteEntities = false;
// load the XML data from the string
$dom->loadXML(ltrim(substr($this->chunks['iTXt'], 17), "\x00"));
// set the encoding to UTF-8
$dom->encoding = 'UTF-8';
// check if the root node of the XML document is of type x:xmpmeta
if ($dom->documentElement->nodeName !== 'x:xmpmeta') {
error_log('ExtractRoot node must be of type x:xmpmeta.');

return;
}
// extract the metadata from the XML document
if (!empty($result = $this->flatten($this->extractNodesXML($dom->documentElement)))) {
// store the metadata in the PNGMetadata::$metadata property
$this->metadata['xmp'] = $result;
}
}
Expand All @@ -542,14 +609,20 @@ private function extractXMP(): void
*/
private function flatten(array $array): array
{
// Loop through each key in the array
foreach ($array as $key => $value) {
// If the value is an array
if (is_array($value)) {
// If the array has only one key, and that key is 0
if (isset($value[0]) && \count($value) === 1) {
// Set the value of this key to be the value of key 0
$array[$key] = $value[0];
// If the new value is an array, call flatten again to flatten it
if (is_array($array[$key])) {
$array[$key] = $this->flatten($array[$key]);
}
} else {
// If the array doesn't have only one key, call flatten again to flatten it
$array[$key] = $this->flatten($value);
}
}
Expand All @@ -568,17 +641,24 @@ private function flatten(array $array): array
*/
private function arrayMerge(array $baseArray, array $array): array
{
// Loop through the array to be merged.
foreach ($array as $key => $value) {
// If the value is an object, get the value of the object.
if (is_object($value)) {
$value = $value->value;
}

// If the key already exists in the base array, merge the values.
if (isset($baseArray[$key])) {
// If the value is an array, merge the arrays.
if (is_array($value)) {
$baseArray[$key] = $this->arrayMerge($baseArray[$key], $array[$key]);
} elseif ($baseArray[$key] !== $value) {
// If the value is not an array, concatenate the values.
$baseArray[$key] .= ',' . $value;
}
} else {
// If the key does not exist, create the key and set the value.
$baseArray[$key] = $value;
}
}
Expand Down

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