Resize image in custom ViewHelper - typo3

Question

I have a ViewHelper that processes some images. I have an image path to an original file. I need to resize this image.
Is there a PHP code I can use in TYPO3 to do this?
I tried this:
$imgPath = 'img/path/from_database.jpg
$imgConf = array();
$imgConf['file'] = $imgPath;
$imgConf['altText'] = "Sample alt text.";
$image = $this->cObj->IMAGE($imgConf);
but I'm getting this exception: "Call to a member function IMAGE() on null"
My ViewHelper inherits from: \TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper

Answer 1

First of all you should say what TYPO3 version you use and if your extension uses Extbase or the old pibased code.
I guess it's Extbase since you inherit from a namespaced viewhelper. My advice would be to take a look at the original f:image viewhelper code (TYPO3\CMS\Fluid\ViewHelpers\ImageViewHelper) and copy what you need.
first add this to the top part of you viewhelper:
/**
* #var \TYPO3\CMS\Extbase\Service\ImageService
* #inject
*/
protected $imageService;
Then the code in your method
$image = $this->imageService->getImage($imgPath);
// you have to set these variables or remove if you don't need them
$processingInstructions = array(
'width' => $width,
'height' => $height,
'minWidth' => $minWidth,
'minHeight' => $minHeight,
'maxWidth' => $maxWidth,
'maxHeight' => $maxHeight,
'crop' => $crop,
);
$processedImage = $this->imageService->applyProcessingInstructions($image, $processingInstructions);
$imageUri = $this->imageService->getImageUri($processedImage);
$imageUri now holds the path to the resized image.
PS: The example you copied is from the old pibased system that no longer exists since the 7.x branch.