WP_Image_Editor_Imagick::thumbnail_image() │ protected │ WP 4.5.0

Efficiently resize the current image

This is a WordPress specific implementation of Imagick::thumbnailImage(), which resizes an image to given dimensions and removes any associated profiles.

Method of the class: WP_Image_Editor_Imagick{}

Return

null|WP_Error.

Usage

// protected - for code of main (parent) or child class
$result = $this->thumbnail_image( $dst_w, $dst_h, $filter_name, $strip_meta );

$dst_w(int) (required)

The destination width.

$dst_h(int) (required)

The destination height.

$filter_name(string)

The Imagick filter to use when resizing.
Default: 'FILTER_TRIANGLE'

$strip_meta(true|false)

Strip all profiles, excluding color profiles, from the image.
Default: true

Changelog

WP_Image_Editor_Imagick::thumbnail_image() WP Image Editor Imagick::thumbnail image code ^{WP 6.5.2}

protected function thumbnail_image( $dst_w, $dst_h, $filter_name = 'FILTER_TRIANGLE', $strip_meta = true ) {
	$allowed_filters = array(
		'FILTER_POINT',
		'FILTER_BOX',
		'FILTER_TRIANGLE',
		'FILTER_HERMITE',
		'FILTER_HANNING',
		'FILTER_HAMMING',
		'FILTER_BLACKMAN',
		'FILTER_GAUSSIAN',
		'FILTER_QUADRATIC',
		'FILTER_CUBIC',
		'FILTER_CATROM',
		'FILTER_MITCHELL',
		'FILTER_LANCZOS',
		'FILTER_BESSEL',
		'FILTER_SINC',
	);

	/**
	 * Set the filter value if '$filter_name' name is in the allowed list and the related
	 * Imagick constant is defined or fall back to the default filter.
	 */
	if ( in_array( $filter_name, $allowed_filters, true ) && defined( 'Imagick::' . $filter_name ) ) {
		$filter = constant( 'Imagick::' . $filter_name );
	} else {
		$filter = defined( 'Imagick::FILTER_TRIANGLE' ) ? Imagick::FILTER_TRIANGLE : false;
	}

	/**
	 * Filters whether to strip metadata from images when they're resized.
	 *
	 * This filter only applies when resizing using the Imagick editor since GD
	 * always strips profiles by default.
	 *
	 * @since 4.5.0
	 *
	 * @param bool $strip_meta Whether to strip image metadata during resizing. Default true.
	 */
	if ( apply_filters( 'image_strip_meta', $strip_meta ) ) {
		$this->strip_meta(); // Fail silently if not supported.
	}

	try {
		/*
		 * To be more efficient, resample large images to 5x the destination size before resizing
		 * whenever the output size is less that 1/3 of the original image size (1/3^2 ~= .111),
		 * unless we would be resampling to a scale smaller than 128x128.
		 */
		if ( is_callable( array( $this->image, 'sampleImage' ) ) ) {
			$resize_ratio  = ( $dst_w / $this->size['width'] ) * ( $dst_h / $this->size['height'] );
			$sample_factor = 5;

			if ( $resize_ratio < .111 && ( $dst_w * $sample_factor > 128 && $dst_h * $sample_factor > 128 ) ) {
				$this->image->sampleImage( $dst_w * $sample_factor, $dst_h * $sample_factor );
			}
		}

		/*
		 * Use resizeImage() when it's available and a valid filter value is set.
		 * Otherwise, fall back to the scaleImage() method for resizing, which
		 * results in better image quality over resizeImage() with default filter
		 * settings and retains backward compatibility with pre 4.5 functionality.
		 */
		if ( is_callable( array( $this->image, 'resizeImage' ) ) && $filter ) {
			$this->image->setOption( 'filter:support', '2.0' );
			$this->image->resizeImage( $dst_w, $dst_h, $filter, 1 );
		} else {
			$this->image->scaleImage( $dst_w, $dst_h );
		}

		// Set appropriate quality settings after resizing.
		if ( 'image/jpeg' === $this->mime_type ) {
			if ( is_callable( array( $this->image, 'unsharpMaskImage' ) ) ) {
				$this->image->unsharpMaskImage( 0.25, 0.25, 8, 0.065 );
			}

			$this->image->setOption( 'jpeg:fancy-upsampling', 'off' );
		}

		if ( 'image/png' === $this->mime_type ) {
			$this->image->setOption( 'png:compression-filter', '5' );
			$this->image->setOption( 'png:compression-level', '9' );
			$this->image->setOption( 'png:compression-strategy', '1' );
			$this->image->setOption( 'png:exclude-chunk', 'all' );
		}

		/*
		 * If alpha channel is not defined, set it opaque.
		 *
		 * Note that Imagick::getImageAlphaChannel() is only available if Imagick
		 * has been compiled against ImageMagick version 6.4.0 or newer.
		 */
		if ( is_callable( array( $this->image, 'getImageAlphaChannel' ) )
			&& is_callable( array( $this->image, 'setImageAlphaChannel' ) )
			&& defined( 'Imagick::ALPHACHANNEL_UNDEFINED' )
			&& defined( 'Imagick::ALPHACHANNEL_OPAQUE' )
		) {
			if ( $this->image->getImageAlphaChannel() === Imagick::ALPHACHANNEL_UNDEFINED ) {
				$this->image->setImageAlphaChannel( Imagick::ALPHACHANNEL_OPAQUE );
			}
		}

		// Limit the bit depth of resized images to 8 bits per channel.
		if ( is_callable( array( $this->image, 'getImageDepth' ) ) && is_callable( array( $this->image, 'setImageDepth' ) ) ) {
			if ( 8 < $this->image->getImageDepth() ) {
				$this->image->setImageDepth( 8 );
			}
		}
	} catch ( Exception $e ) {
		return new WP_Error( 'image_resize_error', $e->getMessage() );
	}
}