Magento: ImageCdn bug? (long story) - magento

Question

I have some question related with Magento's free extension OnePica ImageCdn.
A broken image appear in frontend when I uploaded "corrupt image".
Ok, let's start the long story:
I notice it is happened because of ImageCdn extension and "corrupt image".
In some part of ImageCdn's code:
OnePica_ImageCdn_Helper_Image
/**
* In older versions of Magento (<1.1.3) this method was used to get an image URL.
* However, 1.1.3 now uses the getUrl() method in the product > image model. This code
* was added for backwards compatibility.
*
* #return string
*/
public function __toString()
{
parent::__toString();
return $this->_getModel()->getUrl();
}
My question is, anybody know what is the purpose of that code?
I don't understand what is the meaning of their comment above.
I think it is a bug as it always return $this->_getModel()->getUrl();
Is is really a bug or it is just my wrong interpretation?
This is what I've done so far:
I have an image dummy.jpeg
After some investigation, I just realized that is a "corrupt image".
I tested using: <?php print_r(getimagesize('dummy.jpeg')); ?>
Result:
Array
(
[0] => 200
[1] => 200
[2] => 6
[3] => width="200" height="200"
[bits] => 24
[mime] => image/x-ms-bmp
)
Of course I was surprised by the result because it looks good when I open it using Preview (on Mac OSX)
Then I open it using hex editor, the first two bytes is : BM which is BMP's identifier
I tried to upload .bmp image for product -> failed, can not select the image
I asked my colleague to upload it too (on Ubuntu), he was able to change the choices for file type into "any files". When he click "Upload Files", error message shown state that that type of file is not allowed.
What crossed on my mind is: an admin tried to upload .bmp image and failed. Then he rename it into .jpeg and successful. Though I don't get it what kind of images can be renamed without showing broken image logo (out of topic).
Those scenarios trigger an Exception, I'll break down what I've traced.
Trace of the codes:
app/design/frontend/base/default/catalog/product/view/media.phtml
<?php
$_img = '<img id="image" src="'.$this->helper('catalog/image')->init($_product, 'image').'" alt="'.$this->htmlEscape($this->getImageLabel()).'" title="'.$this->htmlEscape($this->getImageLabel()).'" />';
echo $_helper->productAttribute($_product, $_img, 'image');
?>
From that code, I know that image url is generated using: $this->helper('catalog/image')->init($_product, 'image')
I did Mage::log((string)$this->helper('catalog/image')->init($_product, 'image'));
Result:
http://local.m.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/d/u/dummy.jpeg
.
Mage_Catalog_Helper_Image
public function __toString()
{
try {
if( $this->getImageFile() ) {
$this->_getModel()->setBaseFile( $this->getImageFile() );
} else {
$this->_getModel()->setBaseFile( $this->getProduct()->getData($this->_getModel()->getDestinationSubdir()) );
}
if( $this->_getModel()->isCached() ) {
return $this->_getModel()->getUrl();
} else {
if( $this->_scheduleRotate ) {
$this->_getModel()->rotate( $this->getAngle() );
}
if ($this->_scheduleResize) {
$this->_getModel()->resize();
}
if( $this->getWatermark() ) {
$this->_getModel()->setWatermark($this->getWatermark());
}
Mage::log('pass');
$url = $this->_getModel()->saveFile()->getUrl();
Mage::log('not pass');
}
} catch( Exception $e ) {
$url = Mage::getDesign()->getSkinUrl($this->getPlaceholder());
}
return $url;
}
The error triggered in $this->_getModel()->saveFile()->getUrl(). In some part of the code, it will eventually reach:
Varien_Image_Adapter_Gd2
private function _getCallback($callbackType, $fileType = null, $unsupportedText = 'Unsupported image format.')
{
if (null === $fileType) {
$fileType = $this->_fileType;
}
if (empty(self::$_callbacks[$fileType])) {
//reach this line -> exception thrown
throw new Exception($unsupportedText);
}
if (empty(self::$_callbacks[$fileType][$callbackType])) {
throw new Exception('Callback not found.');
}
return self::$_callbacks[$fileType][$callbackType];
}
The exception was catched in the previous code:
Mage_Catalog_Helper_Image
public function __toString()
{
...
} catch( Exception $e ) {
$url = Mage::getDesign()->getSkinUrl($this->getPlaceholder());
}
...
}
the $url became:
http://local.m.com/skin/frontend/default/default/images/catalog/product/placeholder/image.jpg
So, it should have generated placeholder image right?
(without ImageCdn extension)
No, because
Mage_Catalog_Helper_Image was rewritten by
OnePica_ImageCdn_Helper_Image
public function __toString()
{
parent::__toString(); //the result is http://local.m.com/skin/frontend/default/default/images/catalog/product/placeholder/image.jpg but no variable store/process its value
return $this->_getModel()->getUrl(); //in the end it will return http://local.m.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/d/u/dummy.jpeg
}
In case you all already forgot the question:
Anybody know what is the purpose of that code? I don't understand what is the meaning of their comment above.
Is it really a bug or it is just my wrong interpretation?

Answer 1

No it isn't a bug. It's just legacy support for older Magento systems. I'm wondering, have you ever got around to snoop around earlier versions of magento (as the inline documentation comment references to, < 1.1.3)?
The gist of the matter is before Mage 1.1.3, Mage_Catalog_Helper_Image instances happen to produce URL's from to-string casts e.g.
$image = (some instance of Mage_Catalog_Helper_Image).. ;
$imageUrl = (string) $image;
__toString is probably either protected or private, i'm not sure but what I'm sure is the usual practice is to always code up this Magic Method in order to use it in a class that you are meaning to rewrite something with that expects to use this kind data cast.