WP_Image_Editor_Imagick::thumbnail_image PHP Method

    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 our whitelist and the related
         * Imagick constant is defined or fall back to our default filter.
         */
        if (in_array($filter_name, $allowed_filters) && 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 < 0.111 && ($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()) {
                    $this->image->setImageDepth(8);
                }
            }
            if (is_callable(array($this->image, 'setInterlaceScheme')) && defined('Imagick::INTERLACE_NO')) {
                $this->image->setInterlaceScheme(Imagick::INTERLACE_NO);
            }
        } catch (Exception $e) {
            return new WP_Error('image_resize_error', $e->getMessage());
        }
    }