Silverstripe Custom Validator on Uploadfield - silverstripe

Question

I am using foresight.js to load hi-res images for retina devices. Foresight attempts to replace lo-res images with 2x-pixel density images. Since foresight attempts to replace lo-res images before the page has rendered, it is not possible for me to use the GD image resizing methods in the template for my resized images. So, I am allowing the SS 3.1 cms user to upload one large image and having the system re-size it after upload - leaving a 1x and 2x image in the assets folder.
My question is how can I set a custom validation error message if the cms user does not upload a large enough image?
Here is the code that resizes the image on upload.
class ResampledImage extends Image {
static $default_lores_x = 250;
static $default_lores_y = 250;
static $default_hires_x = 500;
static $default_hires_y = 500;
static $default_assets_dir = 'Uploads';
static $hires_flag = '2x';
function getLoResX() {
return ( static::$lores_x ) ? static::$lores_x : self::$default_lores_x;
}
function getLoResY() {
return ( static::$lores_y ) ? static::$lores_y : self::$default_lores_y;
}
function getHiResX() {
return ( static::$hires_x ) ? static::$hires_x : self::$default_hires_x;
}
function getHiResY() {
return ( static::$hires_y ) ? static::$hires_y : self::$default_hires_y;
}
function getAssetsDir() {
return ( static::$assets_dir ) ? static::$assets_dir : self::$default_assets_dir;
}
function onAfterUpload() {
$this->createResampledImages();
}
function onAfterWrite() {
$this->createResampledImages();
}
function createResampledImages() {
$extension = strtolower($this->getExtension());
if( $this->getHeight() >= $this->getHiResX() || $this->getWidth() >= $this->getHiResY() ) {
$original = $this->getFullPath();
$resampled = $original. '.tmp.'. $extension;
$orig_title = $this->getTitle();
$path_to_hires = Director::baseFolder() . '/' . ASSETS_DIR . '/' . $this->getAssetsDir();
$hires = $path_to_hires . '/' . $orig_title . self::$hires_flag . '.' . $extension;
$gd_lg = new GD($original);
$gd_sm = new GD($original);
if ( $gd_lg->hasImageResource() ) {
$gd_lg = $gd_lg->resizeRatio($this->getHiResX(), $this->getHiResY());
if ( $gd_lg )
$gd_lg->writeTo($hires);
}
if($gd_sm->hasImageResource()) {
$gd_sm = $gd_sm->resizeRatio($this->getLoResX(), $this->getLoResY());
if($gd_sm) {
$gd_sm->writeTo($resampled);
unlink($original);
rename($resampled, $original);
}
}
}
}
Looking at UploadField::setFileEditValidator() it appears that I can designate a method on my extended Image class to use as a Validator so that I can check for $this->getWidth() and $this->getHeight() and return an error if they are not large enough.
Is this possible?
I tried adding the following method to ResampledImage, but this was unsuccessful:
function MyValidator() {
$valid = true;
if ( $this->getHeight() < $this->getHiResX() || $this->getWidth() < $this->getHiResY() ) {
$this->validationError("Thumbnail",'Please upload a larger image');
$valid = false;
}
return $valid;
}

Answer 1

I think the fileEditValidator is acutally used after the image has been uploaded and is for the EditForm when displayed/edited.
Seems that what you are looking for is validate the Upload. You can set a custom Upload_Validator with setValidator($validator) on your UploadField.
So what I would try is create a custom validator class (maybe named CustomUploadValidator) that extends Upload_Validator (source can be found in the Upload.php file in the framework). So, something along those lines:
$myValidator = new CustomUploadValidator();
$uploadField->setValidator($myValidator);
In your custom validator class maybe create a method isImageLargeEnough() which you would call in the validate() method:
public function validate() {
if(!$this->isImageLargeEnough()) {
$this->errors[] = 'Image size is not large enough';
return false;
}
return parent::validate();
}
In your isImageLargeEnough() you can access the uploaded image through $this->tmpFile. So maybe do something like:
public function isImageLargeEnough()
{
$imageSize = getimagesize( $this->tmpFile["tmp_name"] );
if ($imageSize !== false)
{
if ( $imageSize[0] < 500 || $imageSize[1] < 500 )
{
return false;
}
}
return true;
}
Here the min width/height are hard coded to 500, but you can probably implement a setMinImageSizes method that stores those on a variable in your custom validator class. which could be called like $uploadField->getValidator()->setMinImageSize(543, 876);
None of this is actually tested, but hopefully it can give you some pointers on what to look for.