class Features {}

In this article

Methods

NameDescription
Features::get_item_featuresBinds the width, height, bit depth and number of channels from stored internal features.
Features::get_primary_item_featuresFinds the width, height, bit depth and number of channels of the primary item.

Source

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 = 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;
  }
}

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