class ColorFieldFormatterText

class ColorFieldFormatterText extends FormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'format' => 'hex',
            'opacity' => TRUE,
        ] + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $opacity = $this->getFieldSetting('opacity');
        $elements = [];
        $elements['format'] = [
            '#type' => 'select',
            '#title' => $this->t('Format'),
            '#options' => $this->getColorFormat(),
            '#default_value' => $this->getSetting('format'),
        ];
        if ($opacity) {
            $elements['opacity'] = [
                '#type' => 'checkbox',
                '#title' => $this->t('Display opacity'),
                '#default_value' => $this->getSetting('opacity'),
            ];
        }
        return $elements;
    }
    
    /**
     * This function is used to get the color format.
     *
     * @param string $format
     *   Format is of string type.
     *
     * @return array|string
     *   Returns array or string.
     */
    protected function getColorFormat($format = NULL) {
        $formats = [];
        $formats['hex'] = $this->t('Hex triplet');
        $formats['rgb'] = $this->t('RGB Decimal');
        if ($format) {
            return $formats[$format];
        }
        return $formats;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $opacity = $this->getFieldSetting('opacity');
        $settings = $this->getSettings();
        $summary = [];
        $summary[] = $this->t('@format', [
            '@format' => $this->getColorFormat($settings['format']),
        ]);
        if ($opacity && $settings['opacity']) {
            $summary[] = $this->t('Display with opacity.');
        }
        return $summary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        foreach ($items as $delta => $item) {
            $elements[$delta] = [
                '#markup' => $this->viewValue($item),
            ];
        }
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function viewValue(ColorFieldType $item) {
        $opacity = $this->getFieldSetting('opacity');
        $settings = $this->getSettings();
        $color_hex = new ColorHex($item->color, $item->opacity);
        switch ($settings['format']) {
            case 'hex':
                if ($opacity && $settings['opacity']) {
                    $output = $color_hex->toString(TRUE);
                }
                else {
                    $output = $color_hex->toString(FALSE);
                }
                break;
            case 'rgb':
                if ($opacity && $settings['opacity']) {
                    $output = $color_hex->toRgb()
                        ->toString(TRUE);
                }
                else {
                    $output = $color_hex->toRgb()
                        ->toString(FALSE);
                }
                break;
        }
        return $output;
    }

}