How to get file path to transformed image?

[wsydney76]

Use case: Create and copy special transforms of selected images and package them into a native app, using a local transform filesystem.

This gets more complicated in Craft 4, eg. in Craft 3 there was Craft::$app->assetTransforms->getTransformSubpath(), that is now a protected method in the ImageTransformer class.

Thrown together some wild things in a behavior, learned a lot I never wanted to know, probably missing better approaches, finally feeling uncomfortable with doing all this in detail by myself.

/**
     * Workaround because some file system methods are protected in Craft 4
     *
     * Format: <Transform file system path>/<opt. subpath>/<opt. folder(s)>/<transform string>/<opt. image.id>/<filename>
     *
     * @param $transform
     * @return string|null
     * @throws ImageTransformException
     * @throws InvalidConfigException
     */
    public function getImageTransformPath(string|array $transform): ?string
    {
        /** @var Asset $image */
        $image = $this->owner;

        // Get base path of transform filesystem
        $path = App::parseEnv($image->volume->getTransformFs()->path) . DIRECTORY_SEPARATOR;

        // Add subpath, if defined in volume
        if ($image->volume->transformSubpath) {
            $path .= $image->volume->transformSubpath . DIRECTORY_SEPARATOR;
        }

        // If image is in a subfolder, add path to the folder (has trailing slash ??)
        $folder = $image->folder->path;
        if ($folder) {
            $path .= $folder;
        }

        // Get transform index record
        /** @var ImageTransformer $transformer */
        $transformer = Craft::$app->imageTransforms->getImageTransformer(ImageTransformer::class);
        $transformIndex = $transformer->getTransformIndex($image, $transform);

        // Add transform string to path (_transformName or _<width>x<height>_<mode>_<pos>_none)
        $path .= $transformIndex->transformString . DIRECTORY_SEPARATOR;

        // Asset is in subfolder <id> if it has a different filename than original image (if format is different)
        if ($image->filename != $transformIndex->filename) {
            $path .= $image->id . DIRECTORY_SEPARATOR;
        }

        // Finally: Add filename of transformed image
        $path .= $transformIndex->filename;

        if (!file_exists($path)) {
            return null;
        }

        return $path;
    }

So it would be great to have a public method like ::getTransformedImagePath($asset, $transform)

/Mel

PS.
Finally cheated by just replacing @web with @webroot, but that won't work with other setups e.g. with server aliases.

And it doesn't feel clean to use http calls.

[brandonkelly]

We should make this easier down the road for sure. For now, you can expose getTransformSubpath() as a public method by providing your own ImageTransformer class that extends craft\imagetransforms\ImageTransformer, like so:

namespace my\namespace;

use craft\elements\Asset;
use craft\imagetransforms\ImageTransformer;
use craft\models\ImageTransformIndex;

class MyImageTransformer extends ImageTransformer
{
    public function getTransformSubpath(Asset $asset, ImageTransformIndex $transformIndex): string
    {
        return parent::getTransformSubpath($asset, $transformIndex);
    }
}

Then you can have Craft use your own ImageTransformer class instead of carft\imagetransforms\ImageTransformer using dependency injection from a module’s init() method:

namespace my\namespace;

use Craft;
use craft\imagetransforms\ImageTransformer;
use craft\models\ImageTransformIndex;

// ...

public function init()
{
    // ...

    Craft::$container->set(
        ImageTransformer::class,
        fn($container, $params, $config) => new MyImageTransformer($config),
    );
}

[wsydney76]

@brandonkelly Thanks, that works perfect.

Just out of curiosity (no priority): Does this approach (DI) work for every Craft class or are there limitations?

At first glance it looks like an alternative to using behaviors, adding the possibility to override methods?

[brandonkelly]

It only works in cases where the class is always instantiated via Craft::createObject(). I had to verify that was the case with ImageTransformer before offering it as a suggestion.

If you do come across something you’d like to override with the DI container, which is being instantiated directly (new SomeClass()), feel free to request that we switch over to Craft::createObject(). It’s a non-breaking change to do.