phacility/phabricator · error · Exception

Unable to determine image dimensions with imagesx()/imagesy(

Q: What causes "Unable to determine image dimensions with imagesx()/imagesy(): %s" in phacility/phabricator?

Verify the file outside Phabricator (php -r 'print_r(getimagesize("file"));' or open it in an image viewer) and re-upload a clean copy.

Error message

Unable to determine image dimensions with imagesx()/imagesy(): %s

What it means

PhabricatorFileImageTransform::getImageDimensions() could not obtain usable dimensions from the loaded GD resource: imagesx() or imagesy() returned false, or returned a value <= 0. This runs lazily the first time a transform needs the source dimensions, so the failure surfaces as soon as any transform math touches a broken bitmap.

Source

Thrown at src/applications/files/transform/PhabricatorFileImageTransform.php:235


  /**
   * Get the pixel dimensions of the image being transformed.
   *
   * @return list<int, int> Width and height of the image.
   */
  protected function getImageDimensions() {
    if ($this->imageX === null) {
      $image = $this->getImage();

      $trap = new PhutilErrorTrap();
      $x = @imagesx($image);
      $y = @imagesy($image);
      $errors = $trap->getErrorsAsString();
      $trap->destroy();

      if (($x === false) || ($y === false) || ($x <= 0) || ($y <= 0)) {
        throw new Exception(
          pht(
            'Unable to determine image dimensions with '.
            'imagesx()/imagesy(): %s',
            $errors));
      }

      $this->imageX = $x;
      $this->imageY = $y;
    }

    return array($this->imageX, $this->imageY);
  }


  /**
   * Get the raw file data for the image being transformed.
   *
   * @return string Raw file data.

View on GitHub (pinned to 5720a38cfe)

Solutions

Verify the file outside Phabricator (php -r 'print_r(getimagesize("file"));' or open it in an image viewer) and re-upload a clean copy.
In custom subclasses, never assign anything but a GD resource returned by imagecreatefromstring() to the image property.
Catch the exception at transform time and skip transforms for files that fail, keeping the original.

Defensive patterns

Strategy: try-catch

Validate before calling

$info = @getimagesize($file->getURI());
if ($info === false || $info[0] <= 0 || $info[1] <= 0) {
  return null; // not transformable
}

Type guard

function hasUsableDimensions($info): bool {
  return is_array($info) && $info[0] > 0 && $info[1] > 0;
}

Try / catch

try {
  list($x, $y) = $transform->getImageDimensions();
} catch (Exception $ex) {
  return null; // broken bitmap; skip transform
}

Prevention

Validate uploads with getimagesize() before storing them as images.
In custom subclasses, only ever assign imagecreatefromstring() results to the image resource.
Skip transforms for files that fail dimension probing rather than retrying them.

When it happens

Trigger: Transforming a file that earlier passed imagecreatefromstring() but whose resource reports no positive dimensions — corrupted decode, truncated pixel data, or (in custom code) a non-image resource placed into $this->image.

Common situations: Partially corrupted uploads (interrupted transfer) that still decode; files with crafted headers; custom transform subclasses that manipulate or replace the internal image resource with something invalid.

Related errors

AI-assisted analysis of phacility/phabricator@5720a38cfe (2026-08-21). Data as JSON: /api/errors/b2248112662bac3b. Report an issue: GitHub.