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/home/tahkoom/public_html/wp-includes/class-avif-info.php
<?php
/**
* Copyright (c) 2021, Alliance for Open Media. All rights reserved
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*
* Note: this class is from libavifinfo - https://aomedia.googlesource.com/libavifinfo/+/refs/heads/main/avifinfo.php at f509487.
* It is used as a fallback to parse AVIF files when the server doesn't support AVIF,
* primarily to identify the width and height of the image.
*
* Note PHP 8.2 added native support for AVIF, so this class can be removed when WordPress requires PHP 8.2.
*/
namespace Avifinfo;
const FOUND = 0; // Input correctly parsed and information retrieved.
const NOT_FOUND = 1; // Input correctly parsed but information is missing or elsewhere.
const TRUNCATED = 2; // Input correctly parsed until missing bytes to continue.
const ABORTED = 3; // Input correctly parsed until stopped to avoid timeout or crash.
const INVALID = 4; // Input incorrectly parsed.
const MAX_SIZE = 4294967295; // Unlikely to be insufficient to parse AVIF headers.
const MAX_NUM_BOXES = 4096; // Be reasonable. Avoid timeouts and out-of-memory.
const MAX_VALUE = 255;
const MAX_TILES = 16;
const MAX_PROPS = 32;
const MAX_FEATURES = 8;
const UNDEFINED = 0; // Value was not yet parsed.
/**
* Reads an unsigned integer with most significant bits first.
*
* @param binary string $input Must be at least $num_bytes-long.
* @param int $num_bytes Number of parsed bytes.
* @return int Value.
*/
function read_big_endian( $input, $num_bytes ) {
if ( $num_bytes == 1 ) {
return unpack( 'C', $input ) [1];
} else if ( $num_bytes == 2 ) {
return unpack( 'n', $input ) [1];
} else if ( $num_bytes == 3 ) {
$bytes = unpack( 'C3', $input );
return ( $bytes[1] << 16 ) | ( $bytes[2] << 8 ) | $bytes[3];
} else { // $num_bytes is 4
// This might fail to read unsigned values >= 2^31 on 32-bit systems.
// See https://www.php.net/manual/en/function.unpack.php#106041
return unpack( 'N', $input ) [1];
}
}
/**
* Reads bytes and advances the stream position by the same count.
*
* @param stream $handle Bytes will be read from this resource.
* @param int $num_bytes Number of bytes read. Must be greater than 0.
* @return binary string|false The raw bytes or false on failure.
*/
function read( $handle, $num_bytes ) {
$data = fread( $handle, $num_bytes );
return ( $data !== false && strlen( $data ) >= $num_bytes ) ? $data : false;
}
/**
* Advances the stream position by the given offset.
*
* @param stream $handle Bytes will be skipped from this resource.
* @param int $num_bytes Number of skipped bytes. Can be 0.
* @return bool True on success or false on failure.
*/
// Skips 'num_bytes' from the 'stream'. 'num_bytes' can be zero.
function skip( $handle, $num_bytes ) {
return ( fseek( $handle, $num_bytes, SEEK_CUR ) == 0 );
}
//------------------------------------------------------------------------------
// Features are parsed into temporary property associations.
class Tile { // Tile item id <-> parent item id associations.
public $tile_item_id;
public $parent_item_id;
}
class Prop { // Property index <-> item id associations.
public $property_index;
public $item_id;
}
class Dim_Prop { // Property <-> features associations.
public $property_index;
public $width;
public $height;
}
class Chan_Prop { // Property <-> features associations.
public $property_index;
public $bit_depth;
public $num_channels;
}
class Features {
public $has_primary_item = false; // True if "pitm" was parsed.
public $has_alpha = false; // True if an alpha "auxC" was parsed.
public $primary_item_id;
public $primary_item_features = array( // Deduced from the data below.
'width' => UNDEFINED, // In number of pixels.
'height' => UNDEFINED, // Ignores mirror and rotation.
'bit_depth' => UNDEFINED, // Likely 8, 10 or 12 bits per channel per pixel.
'num_channels' => UNDEFINED // Likely 1, 2, 3 or 4 channels:
// (1 monochrome or 3 colors) + (0 or 1 alpha)
);
public $tiles = array(); // Tile[]
public $props = array(); // Prop[]
public $dim_props = array(); // Dim_Prop[]
public $chan_props = array(); // Chan_Prop[]
/**
* Binds the width, height, bit depth and number of channels from stored internal features.
*
* @param int $target_item_id Id of the item whose features will be bound.
* @param int $tile_depth Maximum recursion to search within tile-parent relations.
* @return Status FOUND on success or NOT_FOUND on failure.
*/
private function get_item_features( $target_item_id, $tile_depth ) {
foreach ( $this->props as $prop ) {
if ( $prop->item_id != $target_item_id ) {
continue;
}
// Retrieve the width and height of the primary item if not already done.
if ( $target_item_id == $this->primary_item_id &&
( $this->primary_item_features['width'] == UNDEFINED ||
$this->primary_item_features['height'] == UNDEFINED ) ) {
foreach ( $this->dim_props as $dim_prop ) {
if ( $dim_prop->property_index != $prop->property_index ) {
continue;
}
$this->primary_item_features['width'] = $dim_prop->width;
$this->primary_item_features['height'] = $dim_prop->height;
if ( $this->primary_item_features['bit_depth'] != UNDEFINED &&
$this->primary_item_features['num_channels'] != UNDEFINED ) {
return FOUND;
}
break;
}
}
// Retrieve the bit depth and number of channels of the target item if not
// already done.
if ( $this->primary_item_features['bit_depth'] == UNDEFINED ||
$this->primary_item_features['num_channels'] == UNDEFINED ) {
foreach ( $this->chan_props as $chan_prop ) {
if ( $chan_prop->property_index != $prop->property_index ) {
continue;
}
$this->primary_item_features['bit_depth'] = $chan_prop->bit_depth;
$this->primary_item_features['num_channels'] = $chan_prop->num_channels;
if ( $this->primary_item_features['width'] != UNDEFINED &&
$this->primary_item_features['height'] != UNDEFINED ) {
return FOUND;
}
break;
}
}
}
// Check for the bit_depth and num_channels in a tile if not yet found.
if ( $tile_depth < 3 ) {
foreach ( $this->tiles as $tile ) {
if ( $tile->parent_item_id != $target_item_id ) {
continue;
}
$status = $this->get_item_features( $tile->tile_item_id, $tile_depth + 1 );
if ( $status != NOT_FOUND ) {
return $status;
}
}
}
return NOT_FOUND;
}
/**
* Finds the width, height, bit depth and number of channels of the primary item.
*
* @return Status FOUND on success or NOT_FOUND on failure.
*/
public function get_primary_item_features() {
// Nothing to do without the primary item ID.
if ( !$this->has_primary_item ) {
return NOT_FOUND;
}
// Early exit.
if ( empty( $this->dim_props ) || empty( $this->chan_props ) ) {
return NOT_FOUND;
}
$status = $this->get_item_features( $this->primary_item_id, /*tile_depth=*/ 0 );
if ( $status != FOUND ) {
return $status;
}
// "auxC" is parsed before the "ipma" properties so it is known now, if any.
if ( $this->has_alpha ) {
++$this->primary_item_features['num_channels'];
}
return FOUND;
}
}
//------------------------------------------------------------------------------
class Box {
public $size; // In bytes.
public $type; // Four characters.
public $version; // 0 or actual version if this is a full box.
public $flags; // 0 or actual value if this is a full box.
public $content_size; // 'size' minus the header size.
/**
* Reads the box header.
*
* @param stream $handle The resource the header will be parsed from.
* @param int $num_parsed_boxes The total number of parsed boxes. Prevents timeouts.
* @param int $num_remaining_bytes The number of bytes that should be available from the resource.
* @return Status FOUND on success or an error on failure.
*/
public function parse( $handle, &$num_parsed_boxes, $num_remaining_bytes = MAX_SIZE ) {
// See ISO/IEC 14496-12:2012(E) 4.2
$header_size = 8; // box 32b size + 32b type (at least)
if ( $header_size > $num_remaining_bytes ) {
return INVALID;
}
if ( !( $data = read( $handle, 8 ) ) ) {
return TRUNCATED;
}
$this->size = read_big_endian( $data, 4 );
$this->type = substr( $data, 4, 4 );
// 'box->size==1' means 64-bit size should be read after the box type.
// 'box->size==0' means this box extends to all remaining bytes.
if ( $this->size == 1 ) {
$header_size += 8;
if ( $header_size > $num_remaining_bytes ) {
return INVALID;
}
if ( !( $data = read( $handle, 8 ) ) ) {
return TRUNCATED;
}
// Stop the parsing if any box has a size greater than 4GB.
if ( read_big_endian( $data, 4 ) != 0 ) {
return ABORTED;
}
// Read the 32 least-significant bits.
$this->size = read_big_endian( substr( $data, 4, 4 ), 4 );
} else if ( $this->size == 0 ) {
$this->size = $num_remaining_bytes;
}
if ( $this->size < $header_size ) {
return INVALID;
}
if ( $this->size > $num_remaining_bytes ) {
return INVALID;
}
$has_fullbox_header = $this->type == 'meta' || $this->type == 'pitm' ||
$this->type == 'ipma' || $this->type == 'ispe' ||
$this->type == 'pixi' || $this->type == 'iref' ||
$this->type == 'auxC';
if ( $has_fullbox_header ) {
$header_size += 4;
}
if ( $this->size < $header_size ) {
return INVALID;
}
$this->content_size = $this->size - $header_size;
// Avoid timeouts. The maximum number of parsed boxes is arbitrary.
++$num_parsed_boxes;
if ( $num_parsed_boxes >= MAX_NUM_BOXES ) {
return ABORTED;
}
$this->version = 0;
$this->flags = 0;
if ( $has_fullbox_header ) {
if ( !( $data = read( $handle, 4 ) ) ) {
return TRUNCATED;
}
$this->version = read_big_endian( $data, 1 );
$this->flags = read_big_endian( substr( $data, 1, 3 ), 3 );
// See AV1 Image File Format (AVIF) 8.1
// at https://aomediacodec.github.io/av1-avif/#avif-boxes (available when
// https://github.com/AOMediaCodec/av1-avif/pull/170 is merged).
$is_parsable = ( $this->type == 'meta' && $this->version <= 0 ) ||
( $this->type == 'pitm' && $this->version <= 1 ) ||
( $this->type == 'ipma' && $this->version <= 1 ) ||
( $this->type == 'ispe' && $this->version <= 0 ) ||
( $this->type == 'pixi' && $this->version <= 0 ) ||
( $this->type == 'iref' && $this->version <= 1 ) ||
( $this->type == 'auxC' && $this->version <= 0 );
// Instead of considering this file as invalid, skip unparsable boxes.
if ( !$is_parsable ) {
$this->type = 'unknownversion';
}
}
// print_r( $this ); // Uncomment to print all boxes.
return FOUND;
}
}
//------------------------------------------------------------------------------
class Parser {
private $handle; // Input stream.
private $num_parsed_boxes = 0;
private $data_was_skipped = false;
public $features;
function __construct( $handle ) {
$this->handle = $handle;
$this->features = new Features();
}
/**
* Parses an "ipco" box.
*
* "ispe" is used for width and height, "pixi" and "av1C" are used for bit depth
* and number of channels, and "auxC" is used for alpha.
*
* @param stream $handle The resource the box will be parsed from.
* @param int $num_remaining_bytes The number of bytes that should be available from the resource.
* @return Status FOUND on success or an error on failure.
*/
private function parse_ipco( $num_remaining_bytes ) {
$box_index = 1; // 1-based index. Used for iterating over properties.
do {
$box = new Box();
$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
if ( $status != FOUND ) {
return $status;
}
if ( $box->type == 'ispe' ) {
// See ISO/IEC 23008-12:2017(E) 6.5.3.2
if ( $box->content_size < 8 ) {
return INVALID;
}
if ( !( $data = read( $this->handle, 8 ) ) ) {
return TRUNCATED;
}
$width = read_big_endian( substr( $data, 0, 4 ), 4 );
$height = read_big_endian( substr( $data, 4, 4 ), 4 );
if ( $width == 0 || $height == 0 ) {
return INVALID;
}
if ( count( $this->features->dim_props ) <= MAX_FEATURES &&
$box_index <= MAX_VALUE ) {
$dim_prop_count = count( $this->features->dim_props );
$this->features->dim_props[$dim_prop_count] = new Dim_Prop();
$this->features->dim_props[$dim_prop_count]->property_index = $box_index;
$this->features->dim_props[$dim_prop_count]->width = $width;
$this->features->dim_props[$dim_prop_count]->height = $height;
} else {
$this->data_was_skipped = true;
}
if ( !skip( $this->handle, $box->content_size - 8 ) ) {
return TRUNCATED;
}
} else if ( $box->type == 'pixi' ) {
// See ISO/IEC 23008-12:2017(E) 6.5.6.2
if ( $box->content_size < 1 ) {
return INVALID;
}
if ( !( $data = read( $this->handle, 1 ) ) ) {
return TRUNCATED;
}
$num_channels = read_big_endian( $data, 1 );
if ( $num_channels < 1 ) {
return INVALID;
}
if ( $box->content_size < 1 + $num_channels ) {
return INVALID;
}
if ( !( $data = read( $this->handle, 1 ) ) ) {
return TRUNCATED;
}
$bit_depth = read_big_endian( $data, 1 );
if ( $bit_depth < 1 ) {
return INVALID;
}
for ( $i = 1; $i < $num_channels; ++$i ) {
if ( !( $data = read( $this->handle, 1 ) ) ) {
return TRUNCATED;
}
// Bit depth should be the same for all channels.
if ( read_big_endian( $data, 1 ) != $bit_depth ) {
return INVALID;
}
if ( $i > 32 ) {
return ABORTED; // Be reasonable.
}
}
if ( count( $this->features->chan_props ) <= MAX_FEATURES &&
$box_index <= MAX_VALUE && $bit_depth <= MAX_VALUE &&
$num_channels <= MAX_VALUE ) {
$chan_prop_count = count( $this->features->chan_props );
$this->features->chan_props[$chan_prop_count] = new Chan_Prop();
$this->features->chan_props[$chan_prop_count]->property_index = $box_index;
$this->features->chan_props[$chan_prop_count]->bit_depth = $bit_depth;
$this->features->chan_props[$chan_prop_count]->num_channels = $num_channels;
} else {
$this->data_was_skipped = true;
}
if ( !skip( $this->handle, $box->content_size - ( 1 + $num_channels ) ) ) {
return TRUNCATED;
}
} else if ( $box->type == 'av1C' ) {
// See AV1 Codec ISO Media File Format Binding 2.3.1
// at https://aomediacodec.github.io/av1-isobmff/#av1c
// Only parse the necessary third byte. Assume that the others are valid.
if ( $box->content_size < 3 ) {
return INVALID;
}
if ( !( $data = read( $this->handle, 3 ) ) ) {
return TRUNCATED;
}
$byte = read_big_endian( substr( $data, 2, 1 ), 1 );
$high_bitdepth = ( $byte & 0x40 ) != 0;
$twelve_bit = ( $byte & 0x20 ) != 0;
$monochrome = ( $byte & 0x10 ) != 0;
if ( $twelve_bit && !$high_bitdepth ) {
return INVALID;
}
if ( count( $this->features->chan_props ) <= MAX_FEATURES &&
$box_index <= MAX_VALUE ) {
$chan_prop_count = count( $this->features->chan_props );
$this->features->chan_props[$chan_prop_count] = new Chan_Prop();
$this->features->chan_props[$chan_prop_count]->property_index = $box_index;
$this->features->chan_props[$chan_prop_count]->bit_depth =
$high_bitdepth ? $twelve_bit ? 12 : 10 : 8;
$this->features->chan_props[$chan_prop_count]->num_channels = $monochrome ? 1 : 3;
} else {
$this->data_was_skipped = true;
}
if ( !skip( $this->handle, $box->content_size - 3 ) ) {
return TRUNCATED;
}
} else if ( $box->type == 'auxC' ) {
// See AV1 Image File Format (AVIF) 4
// at https://aomediacodec.github.io/av1-avif/#auxiliary-images
$kAlphaStr = "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0";
$kAlphaStrLength = 44; // Includes terminating character.
if ( $box->content_size >= $kAlphaStrLength ) {
if ( !( $data = read( $this->handle, $kAlphaStrLength ) ) ) {
return TRUNCATED;
}
if ( substr( $data, 0, $kAlphaStrLength ) == $kAlphaStr ) {
// Note: It is unlikely but it is possible that this alpha plane does
// not belong to the primary item or a tile. Ignore this issue.
$this->features->has_alpha = true;
}
if ( !skip( $this->handle, $box->content_size - $kAlphaStrLength ) ) {
return TRUNCATED;
}
} else {
if ( !skip( $this->handle, $box->content_size ) ) {
return TRUNCATED;
}
}
} else {
if ( !skip( $this->handle, $box->content_size ) ) {
return TRUNCATED;
}
}
++$box_index;
$num_remaining_bytes -= $box->size;
} while ( $num_remaining_bytes > 0 );
return NOT_FOUND;
}
/**
* Parses an "iprp" box.
*
* The "ipco" box contain the properties which are linked to items by the "ipma" box.
*
* @param stream $handle The resource the box will be parsed from.
* @param int $num_remaining_bytes The number of bytes that should be available from the resource.
* @return Status FOUND on success or an error on failure.
*/
private function parse_iprp( $num_remaining_bytes ) {
do {
$box = new Box();
$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
if ( $status != FOUND ) {
return $status;
}
if ( $box->type == 'ipco' ) {
$status = $this->parse_ipco( $box->content_size );
if ( $status != NOT_FOUND ) {
return $status;
}
} else if ( $box->type == 'ipma' ) {
// See ISO/IEC 23008-12:2017(E) 9.3.2
$num_read_bytes = 4;
if ( $box->content_size < $num_read_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $num_read_bytes ) ) ) {
return TRUNCATED;
}
$entry_count = read_big_endian( $data, 4 );
$id_num_bytes = ( $box->version < 1 ) ? 2 : 4;
$index_num_bytes = ( $box->flags & 1 ) ? 2 : 1;
$essential_bit_mask = ( $box->flags & 1 ) ? 0x8000 : 0x80;
for ( $entry = 0; $entry < $entry_count; ++$entry ) {
if ( $entry >= MAX_PROPS ||
count( $this->features->props ) >= MAX_PROPS ) {
$this->data_was_skipped = true;
break;
}
$num_read_bytes += $id_num_bytes + 1;
if ( $box->content_size < $num_read_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $id_num_bytes + 1 ) ) ) {
return TRUNCATED;
}
$item_id = read_big_endian(
substr( $data, 0, $id_num_bytes ), $id_num_bytes );
$association_count = read_big_endian(
substr( $data, $id_num_bytes, 1 ), 1 );
for ( $property = 0; $property < $association_count; ++$property ) {
if ( $property >= MAX_PROPS ||
count( $this->features->props ) >= MAX_PROPS ) {
$this->data_was_skipped = true;
break;
}
$num_read_bytes += $index_num_bytes;
if ( $box->content_size < $num_read_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $index_num_bytes ) ) ) {
return TRUNCATED;
}
$value = read_big_endian( $data, $index_num_bytes );
// $essential = ($value & $essential_bit_mask); // Unused.
$property_index = ( $value & ~$essential_bit_mask );
if ( $property_index <= MAX_VALUE && $item_id <= MAX_VALUE ) {
$prop_count = count( $this->features->props );
$this->features->props[$prop_count] = new Prop();
$this->features->props[$prop_count]->property_index = $property_index;
$this->features->props[$prop_count]->item_id = $item_id;
} else {
$this->data_was_skipped = true;
}
}
if ( $property < $association_count ) {
break; // Do not read garbage.
}
}
// If all features are available now, do not look further.
$status = $this->features->get_primary_item_features();
if ( $status != NOT_FOUND ) {
return $status;
}
// Mostly if 'data_was_skipped'.
if ( !skip( $this->handle, $box->content_size - $num_read_bytes ) ) {
return TRUNCATED;
}
} else {
if ( !skip( $this->handle, $box->content_size ) ) {
return TRUNCATED;
}
}
$num_remaining_bytes -= $box->size;
} while ( $num_remaining_bytes > 0 );
return NOT_FOUND;
}
/**
* Parses an "iref" box.
*
* The "dimg" boxes contain links between tiles and their parent items, which
* can be used to infer bit depth and number of channels for the primary item
* when the latter does not have these properties.
*
* @param stream $handle The resource the box will be parsed from.
* @param int $num_remaining_bytes The number of bytes that should be available from the resource.
* @return Status FOUND on success or an error on failure.
*/
private function parse_iref( $num_remaining_bytes ) {
do {
$box = new Box();
$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
if ( $status != FOUND ) {
return $status;
}
if ( $box->type == 'dimg' ) {
// See ISO/IEC 14496-12:2015(E) 8.11.12.2
$num_bytes_per_id = ( $box->version == 0 ) ? 2 : 4;
$num_read_bytes = $num_bytes_per_id + 2;
if ( $box->content_size < $num_read_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $num_read_bytes ) ) ) {
return TRUNCATED;
}
$from_item_id = read_big_endian( $data, $num_bytes_per_id );
$reference_count = read_big_endian( substr( $data, $num_bytes_per_id, 2 ), 2 );
for ( $i = 0; $i < $reference_count; ++$i ) {
if ( $i >= MAX_TILES ) {
$this->data_was_skipped = true;
break;
}
$num_read_bytes += $num_bytes_per_id;
if ( $box->content_size < $num_read_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $num_bytes_per_id ) ) ) {
return TRUNCATED;
}
$to_item_id = read_big_endian( $data, $num_bytes_per_id );
$tile_count = count( $this->features->tiles );
if ( $from_item_id <= MAX_VALUE && $to_item_id <= MAX_VALUE &&
$tile_count < MAX_TILES ) {
$this->features->tiles[$tile_count] = new Tile();
$this->features->tiles[$tile_count]->tile_item_id = $to_item_id;
$this->features->tiles[$tile_count]->parent_item_id = $from_item_id;
} else {
$this->data_was_skipped = true;
}
}
// If all features are available now, do not look further.
$status = $this->features->get_primary_item_features();
if ( $status != NOT_FOUND ) {
return $status;
}
// Mostly if 'data_was_skipped'.
if ( !skip( $this->handle, $box->content_size - $num_read_bytes ) ) {
return TRUNCATED;
}
} else {
if ( !skip( $this->handle, $box->content_size ) ) {
return TRUNCATED;
}
}
$num_remaining_bytes -= $box->size;
} while ( $num_remaining_bytes > 0 );
return NOT_FOUND;
}
/**
* Parses a "meta" box.
*
* It looks for the primary item ID in the "pitm" box and recurses into other boxes
* to find its features.
*
* @param stream $handle The resource the box will be parsed from.
* @param int $num_remaining_bytes The number of bytes that should be available from the resource.
* @return Status FOUND on success or an error on failure.
*/
private function parse_meta( $num_remaining_bytes ) {
do {
$box = new Box();
$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
if ( $status != FOUND ) {
return $status;
}
if ( $box->type == 'pitm' ) {
// See ISO/IEC 14496-12:2015(E) 8.11.4.2
$num_bytes_per_id = ( $box->version == 0 ) ? 2 : 4;
if ( $num_bytes_per_id > $num_remaining_bytes ) {
return INVALID;
}
if ( !( $data = read( $this->handle, $num_bytes_per_id ) ) ) {
return TRUNCATED;
}
$primary_item_id = read_big_endian( $data, $num_bytes_per_id );
if ( $primary_item_id > MAX_VALUE ) {
return ABORTED;
}
$this->features->has_primary_item = true;
$this->features->primary_item_id = $primary_item_id;
if ( !skip( $this->handle, $box->content_size - $num_bytes_per_id ) ) {
return TRUNCATED;
}
} else if ( $box->type == 'iprp' ) {
$status = $this->parse_iprp( $box->content_size );
if ( $status != NOT_FOUND ) {
return $status;
}
} else if ( $box->type == 'iref' ) {
$status = $this->parse_iref( $box->content_size );
if ( $status != NOT_FOUND ) {
return $status;
}
} else {
if ( !skip( $this->handle, $box->content_size ) ) {
return TRUNCATED;
}
}
$num_remaining_bytes -= $box->size;
} while ( $num_remaining_bytes != 0 );
// According to ISO/IEC 14496-12:2012(E) 8.11.1.1 there is at most one "meta".
return INVALID;
}
/**
* Parses a file stream.
*
* The file type is checked through the "ftyp" box.
*
* @return bool True if the input stream is an AVIF bitstream or false.
*/
public function parse_ftyp() {
$box = new Box();
$status = $box->parse( $this->handle, $this->num_parsed_boxes );
if ( $status != FOUND ) {
return false;
}
if ( $box->type != 'ftyp' ) {
return false;
}
// Iterate over brands. See ISO/IEC 14496-12:2012(E) 4.3.1
if ( $box->content_size < 8 ) {
return false;
}
for ( $i = 0; $i + 4 <= $box->content_size; $i += 4 ) {
if ( !( $data = read( $this->handle, 4 ) ) ) {
return false;
}
if ( $i == 4 ) {
continue; // Skip minor_version.
}
if ( substr( $data, 0, 4 ) == 'avif' || substr( $data, 0, 4 ) == 'avis' ) {
return skip( $this->handle, $box->content_size - ( $i + 4 ) );
}
if ( $i > 32 * 4 ) {
return false; // Be reasonable.
}
}
return false; // No AVIF brand no good.
}
/**
* Parses a file stream.
*
* Features are extracted from the "meta" box.
*
* @return bool True if the main features of the primary item were parsed or false.
*/
public function parse_file() {
$box = new Box();
while ( $box->parse( $this->handle, $this->num_parsed_boxes ) == FOUND ) {
if ( $box->type === 'meta' ) {
if ( $this->parse_meta( $box->content_size ) != FOUND ) {
return false;
}
return true;
}
if ( !skip( $this->handle, $box->content_size ) ) {
return false;
}
}
return false; // No "meta" no good.
}
}
الذكاء الاصطناعي التوليدي ابتكار مذهل أم تهديد خفي – tahkoom.com
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الذكاء الاصطناعي التوليدي سلاح ذو حدين
أجرت شركة مايكروسوفت بالتعاون مع جامعة كارنيجي ميلون دراسة حديثة تقدم لنا إجابة حول تأثير الذكاء الاصطناعي التوليدي على المستخدمين حيث أشارت
كيف نحافظ على عقولنا وسط سيطرة الآلات
لاستخدام الذكاء الاصطناعي التوليدي بطريقة صحيحة علينا اتباع عدة خطوات أساسية منها المحافظة على خصوصية بياناتنا بالإضافة إلى عدم مشاركته في أمور تتعلق بحياتنا الشخصية كما يجب علينا استخدام الذكاء الاصطناعي كأداة مساعدة لإنجاز بعض المهام وليس كبديل للعقل فعلى سبيل المثال عند الاستعانة بالذكاء الاصطناعي لإنجاز مهمة معينة يمكننا إضافة تعديلاتنا الخاصة كما يجب علينا مراجعة دقة المعلومات المقدمة بواسطة الذكاء الاصطناعي لأن من الممكن أن تكون مندثه أو غير صحيحة
اوضح الدكتور إبراهيم عبدالله أستاذ تكنولوجيا المعلومات في المعهد العالي للدراسات النوعية في مصر ومعهد البيان للعلوم والتكنولوجيا في الإمارات أن الاعتماد المتزايد على الذكاء الاصطناعي في حياتنا اليومية يحمل في طياته جانب سلبي واخر ايجابي فمن الناحيه السلبية يوجد العديد من التخصصات التي قد تندثر مثل خدمة العملاء والطب وغيرها من التخصصات التي قد تختفي
كما أكد دكتور إبراهيم علي ضرورة إعادة تصميم المناهج الدراسية حتي نكون قادرين علي انتاج الذكاء الاصطناعي وليس فقط مستخدمين كما وجه نصيحة شديدة اللهجة للطلاب الذي تعتمد بشكل كلي علي الذكاء الاصطناعي مؤكد أن ذلك سوف يهدم قدرتهم علي البحث والإنتاج و سيضعف قدراتهم كأفراد بشرية على أعمار عقولهم
لفت الدكتور إبراهيم نظرنا الي إحد إخطر المشكلات التي قد تواجهنا في المستقبل ان الذكاء الاصطناعي يدرك نفسه ويشعر بوجوده ويتحكم في الناس وقراراتهم لصالح مجموعه من الأشخاص او الشراكات او لصالحه هو شخصي
قال الدكتور كريم محمود أستاذ مساعد الذكاء الاصطناعي في معهد ا البيان للعلوم والتكنولوجيا إن الذكاء الاصطناعي التوليدي يمثل فرصة فريدة لتعزيز الإبداع البشري لكنه يحمل في طياته مخاطر أهمها تقليل الاعتماد على العقل والتفكير النقدي وذلك في حالة استخدم بشكل مفرط لذلك من الضروري وضع إطار تنظيمي وتعليمي يوجه الاستخدام الأمثل لهذه الأدوات بحيث تظل مساعدة وليست بديل للعقل والتفكير
و يبقي الذكاء الاصطناعي التوليدي سلاح مزدوج يمكن أن يوسع أفاق الإبداع والابتكار لدينا أو قد يؤدي إلى تراجع قدراتنا الإبداعية لذلك علينا أن ندرك أن الذكاء الاصطناعي في جميع أشكاله أداة مساعدة وليست بديل عن العقل كما يجب علينا استخدامه بحكمة لتحقيق التقدم دون الإغفال عن دورنا كأفراد بشرية في التفكير والابتكار
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