core-bundle/src/Resources/contao/library/Contao/Image.php
public function computeResize()
	{
		$resizeCoordinates = System::getContainer()
			->get('contao.image.resize_calculator')
			->calculate(
				$this->prepareResizeConfig(),
				new ImageDimensions(
					new Box($this->fileObj->viewWidth, $this->fileObj->viewHeight),
					$this->fileObj->viewWidth !== $this->fileObj->width
				),
				$this->prepareImportantPart()
			)
		;

		return array
		(
			'width' => $resizeCoordinates->getCropSize()->getWidth(),
			'height' => $resizeCoordinates->getCropSize()->getHeight(),
			'target_x' => -$resizeCoordinates->getCropStart()->getX(),
			'target_y' => -$resizeCoordinates->getCropStart()->getY(),
			'target_width' => $resizeCoordinates->getSize()->getWidth(),
			'target_height' => $resizeCoordinates->getSize()->getHeight(),
		);
	}
public function computeResize()
	{
		$resizeCoordinates = System::getContainer()
			->get('contao.image.resize_calculator')
			->calculate(
				$this->prepareResizeConfig(),
				new ImageDimensions(
					new Box($this->fileObj->viewWidth, $this->fileObj->viewHeight),
					$this->fileObj->viewWidth !== $this->fileObj->width
				),
				$this->prepareImportantPart()
			)
		;

		return array
		(
			'width' => $resizeCoordinates->getCropSize()->getWidth(),
			'height' => $resizeCoordinates->getCropSize()->getHeight(),
			'target_x' => -$resizeCoordinates->getCropStart()->getX(),
			'target_y' => -$resizeCoordinates->getCropStart()->getY(),
			'target_width' => $resizeCoordinates->getSize()->getWidth(),
			'target_height' => $resizeCoordinates->getSize()->getHeight(),
		);
	}
Calculate the resize coordinates

@return array The resize coordinates (width, height, target_x, target_y, target_width, target_height)