class-respimg.php

<?php

/**
 * hacked up version of php-respimg <https://github.com/nwtn/php-respimg>
 *
 * @package wp-respimg
 * @version 0.0.1
 */

/**
 * An Imagick extension to provide better (higher quality, lower file size) image resizes.
 *
 * This class extends Imagick (<http://php.net/manual/en/book.imagick.php>) based on
 * research into optimal image resizing techniques (<https://github.com/nwtn/image-resize-tests>).
 *
 * Using these methods with their default settings should provide image resizing that is
 * visually indistinguishable from Photoshop’s “Save for Web…”, but at lower file sizes.
 *
 * @author		David Newton <david@davidnewton.ca>
 * @copyright	2015 David Newton
 * @license		https://raw.githubusercontent.com/nwtn/php-respimg/master/LICENSE MIT
 * @version		1.0.0
 */

class Respimg extends Imagick {

	/**
	 * Resizes the image using smart defaults for high quality and low file size.
	 *
	 * This function is basically equivalent to:
	 *
	 * $optim == true: `mogrify -path OUTPUT_PATH -filter Triangle -define filter:support=2.0 -thumbnail OUTPUT_WIDTH -unsharp 0.25x0.08+8.3+0.045 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB INPUT_PATH`
	 *
	 * $optim == false: `mogrify -path OUTPUT_PATH -filter Triangle -define filter:support=2.0 -thumbnail OUTPUT_WIDTH -unsharp 0.25x0.25+8+0.065 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB -strip INPUT_PATH`
	 *
	 * @access	public
	 *
	 * @param	integer	$columns		The number of columns in the output image. 0 = maintain aspect ratio based on $rows.
	 * @param	integer	$rows			The number of rows in the output image. 0 = maintain aspect ratio based on $columns.
	 * @param	bool	$optim			Whether you intend to perform optimization on the resulting image. Note that setting this to `true` doesn’t actually perform any optimization.
	 */

	public function smartResize( $columns, $rows, $optim = false ) {

		$this->setOption( 'filter:support', '2.0' );
		$this->thumbnailImage( $columns, $rows, false, false, Imagick::FILTER_TRIANGLE );
		if ( $optim ) {
			$this->unsharpMaskImage( 0.25, 0.08, 8.3, 0.045 );
		} else {
			$this->unsharpMaskImage( 0.25, 0.25, 8, 0.065 );
		}
		$this->posterizeImage( 136, false );
		$this->setImageCompressionQuality( 82 );
		$this->setOption( 'jpeg:fancy-upsampling', 'off' );
		$this->setOption( 'png:compression-filter', '5' );
		$this->setOption( 'png:compression-level', '9' );
		$this->setOption( 'png:compression-strategy', '1' );
		$this->setOption( 'png:exclude-chunk', 'all' );
		$this->setInterlaceScheme( Imagick::INTERLACE_NO );
		$this->setColorspace( Imagick::COLORSPACE_SRGB );
		if ( ! $optim ) {
			$this->stripImage();
		}

	}


	/**
	 * Changes the size of an image to the given dimensions and removes any associated profiles.
	 *
	 * `thumbnailImage` changes the size of an image to the given dimensions and
	 * removes any associated profiles.  The goal is to produce small low cost
	 * thumbnail images suited for display on the Web.
	 *
	 * With the original Imagick thumbnailImage implementation, there is no way to choose a
	 * resampling filter. This class recreates Imagick’s C implementation and adds this
	 * additional feature.
	 *
	 * Note: <https://github.com/mkoppanen/imagick/issues/90> has been filed for this issue.
	 *
	 * @access	public
	 *
	 * @param	integer	$columns		The number of columns in the output image. 0 = maintain aspect ratio based on $rows.
	 * @param	integer	$rows			The number of rows in the output image. 0 = maintain aspect ratio based on $columns.
	 * @param	bool	$bestfit		Treat $columns and $rows as a bounding box in which to fit the image.
	 * @param	bool	$fill			Fill in the bounding box with the background colour.
	 * @param	integer	$filter			The resampling filter to use. Refer to the list of filter constants at <http://php.net/manual/en/imagick.constants.php>.
	 *
	 * @return	bool	Indicates whether the operation was performed successfully.
	 */

	public function thumbnailImage( $columns, $rows, $bestfit = false, $fill = false, $filter = Imagick::FILTER_TRIANGLE ) {

		// sample factor; defined in original ImageMagick thumbnailImage function
		// the scale to which the image should be resized using the `sample` function
		$SampleFactor = 5;

		// filter whitelist
		$filters = array(
			Imagick::FILTER_POINT,
			Imagick::FILTER_BOX,
			Imagick::FILTER_TRIANGLE,
			Imagick::FILTER_HERMITE,
			Imagick::FILTER_HANNING,
			Imagick::FILTER_HAMMING,
			Imagick::FILTER_BLACKMAN,
			Imagick::FILTER_GAUSSIAN,
			Imagick::FILTER_QUADRATIC,
			Imagick::FILTER_CUBIC,
			Imagick::FILTER_CATROM,
			Imagick::FILTER_MITCHELL,
			Imagick::FILTER_LANCZOS,
			Imagick::FILTER_BESSEL,
			Imagick::FILTER_SINC
		);

		// Parse parameters given to function
		$columns = (double) $columns;
		$rows = (double) $rows;
		$bestfit = (bool) $bestfit;
		$fill = (bool) $fill;

		// We can’t resize to (0,0)
		if ( $rows < 1 && $columns < 1 ) {
			return false;
		}

		// Set a default filter if an acceptable one wasn’t passed
		if ( ! in_array( $filter, $filters ) ) {
			$filter = Imagick::FILTER_TRIANGLE;
		}

		// figure out the output width and height
		$width = (double) $this->getImageWidth();
		$height = (double) $this->getImageHeight();
		$new_width = $columns;
		$new_height = $rows;

		$x_factor = $columns / $width;
		$y_factor = $rows / $height;
		if ( $rows < 1 ) {
			$new_height = round( $x_factor * $height );
		} elseif ( $columns < 1 ) {
			$new_width = round( $y_factor * $width );
		}

		// if bestfit is true, the new_width/new_height of the image will be different than
		// the columns/rows parameters; those will define a bounding box in which the image will be fit
		if ( $bestfit && $x_factor > $y_factor ) {
			$x_factor = $y_factor;
			$new_width = round( $y_factor * $width );
		} elseif ( $bestfit && $y_factor > $x_factor ) {
			$y_factor = $x_factor;
			$new_height = round( $x_factor * $height );
		}
		if ( $new_width < 1 ) {
			$new_width = 1;
		}
		if ( $new_height < 1 ) {
			$new_height = 1;
		}

		// if we’re resizing the image to more than about 1/3 it’s original size
		// then just use the resize function
		if ( ( $x_factor * $y_factor ) > 0.1 ) {
			$this->resizeImage( $new_width, $new_height, $filter, 1 );

		// if we’d be using sample to scale to smaller than 128x128, just use resize
		} elseif ( ( ( $SampleFactor * $new_width ) < 128) || ( ( $SampleFactor * $new_height ) < 128 ) ) {
				$this->resizeImage( $new_width, $new_height, $filter, 1 );

		// otherwise, use sample first, then resize
		} else {
			$this->sampleImage( $SampleFactor * $new_width, $SampleFactor * $new_height );
			$this->resizeImage( $new_width, $new_height, $filter, 1 );
		}

		// if the alpha channel is not defined, make it opaque
		if ( $this->getImageAlphaChannel() == Imagick::ALPHACHANNEL_UNDEFINED ) {
			$this->setImageAlphaChannel( Imagick::ALPHACHANNEL_OPAQUE );
		}

		// set the image’s bit depth to 8 bits
		$this->setImageDepth( 8 );

		// turn off interlacing
		$this->setInterlaceScheme( Imagick::INTERLACE_NO );

		// Strip all profiles except color profiles.
		foreach ( $this->getImageProfiles( '*', true ) as $key => $value ) {
			if ( $key != 'icc' && $key != 'icm' ) {
				$this->removeImageProfile( $key );
			}
		}

		if ( method_exists( $this, 'deleteImageProperty' ) ) {
			$this->deleteImageProperty( 'comment' );
			$this->deleteImageProperty( 'Thumb::URI' );
			$this->deleteImageProperty( 'Thumb::MTime' );
			$this->deleteImageProperty( 'Thumb::Size' );
			$this->deleteImageProperty( 'Thumb::Mimetype' );
			$this->deleteImageProperty( 'software' );
			$this->deleteImageProperty( 'Thumb::Image::Width' );
			$this->deleteImageProperty( 'Thumb::Image::Height' );
			$this->deleteImageProperty( 'Thumb::Document::Pages' );
		} else {
			$this->setImageProperty( 'comment', '' );
			$this->setImageProperty( 'Thumb::URI', '' );
			$this->setImageProperty( 'Thumb::MTime', '' );
			$this->setImageProperty( 'Thumb::Size', '' );
			$this->setImageProperty( 'Thumb::Mimetype', '' );
			$this->setImageProperty( 'software', '' );
			$this->setImageProperty( 'Thumb::Image::Width', '' );
			$this->setImageProperty( 'Thumb::Image::Height', '' );
			$this->setImageProperty( 'Thumb::Document::Pages', '' );
		}

		// In case user wants to fill use extent for it rather than creating a new canvas
		// …fill out the bounding box
		if ( $bestfit && $fill && ( $new_width != $columns || $new_height != $rows ) ) {
			$extent_x = 0;
			$extent_y = 0;

			if ( $columns > $new_width ) {
				$extent_x = ( $columns - $new_width ) / 2;
			}

			if ( $rows > $new_height ) {
				$extent_y = ( $rows - $new_height ) / 2;
			}

			$this->extentImage( $columns, $rows, 0 - $extent_x, $extent_y );
		}

		return true;

	}

}