Programmatically Update Image Labels

Question

I'm trying to update my product images' labels. I want them to be the same as the name of the product.

What I've tried

$mediaModel = Mage::getModel("catalog/product_attribute_backend_media");
$images = $product->getMediaGalleryImages();
foreach ($images as $image) {
    $mediaModel->updateImage(
        $product->getId(),
        $image->getFile(),
        array("label" => $title)
    );
}

But then I get this error

Fatal error: Call to a member function getAttributeCode() on a non-object in app/code/core/Mage/Catalog/Model/Product/Attribute/Backend/Media.php on line 401

I've also tried

$mediaModel = Mage::getModel("catalog/product_attribute_media_api");
$images = $mediaModel->items($product->getId());
foreach ($images as $image) {    
    $mediaModel->update(
        $product->getId(),
        $image['file'],
        array("label" => $title)
    );
}

Which runs fine, but the values aren't updated in the admin.

How do I go about this?

Answer 1

The following code should work for you.

$product = mage::getModel('catalog/product')->load(16);
$attributes = $product->getTypeInstance(true)->getSetAttributes($product);
$gallery = $attributes['media_gallery'];
$images = $product->getMediaGalleryImages();
foreach ($images as $image) {
    $backend = $gallery->getBackend();
    $backend->updateImage(
        $product,
        $image->getFile(),
        array('label' => 'Blah')
    );
}
$product->getResource()->saveAttribute($product, 'media_gallery');

I was getting an error on simply $product->save(); but saving the one attribute seems to work.

Answer 2

The above code didn't work for me. Here is the changed code that end up working:

function _SetProductImagesAlt($product, $altText='') {
  if (is_numeric($product))
  {
    $product = mage::getModel('catalog/product')->load($product);
  }
  else //reload the product
  {
    $product = mage::getModel('catalog/product')->load($product->getId());
  }

  //set alt to the name of the Product if not set otherwise
  if (empty($altText))
  {
    $altText = $product->getName();
  }

  //sanitize string
  $altText = str_replace("\r", "", $altText);
  $altText = str_replace("\n", "", $altText);

  $altText = htmlspecialchars($altText, ENT_QUOTES, 'UTF-8');

  $attributes = $product->getTypeInstance(true)->getSetAttributes($product);
  $images = $product->getMediaGalleryImages();
  $mediaGalleryBackendModel = $attributes['media_gallery']->getBackend();
  foreach ($images as $image) {
    $mediaGalleryBackendModel->updateImage($product, $image->getFile(), array('label' => $altText));
  }
  $product->save();   
}

Note: the reloading of the product object in the line 8 turned out to be important if you used the same object to add a new product beforehand.