something like which would output a new url for the new manipulated image file.

Thanks!

Thank you for this, it’s fantastic creating a b/w thumbnail for me. However I’m having trouble with watermarking the full colour images. All plugins I have tried removed the b/w filter when you run the plugin. I cannot stop this from happening and I cannot figure out a way to automate adding a watermark using the function.php and there is no documentation online on how to do this with WordPress…

Do you have any ideas how to do this?

Thanks!

I was having issues with it at first. The issue I had was if you uploaded an image smaller than the image size, you would get an error (undefined index). So I added a conditional to check if that image size was available, and if it wasn’t it used the original image: https://gist.github.com/2952049


function bw_filter($meta) {
$path = wp_upload_dir();
/* get dirname of file to get correct date folder */
$subdir = trailingslashit(dirname($meta['file']));
/* get basedir on path to get uploads folder */
$file = trailingslashit($path['basedir']).$subdir.$meta['sizes']['bw-image']['file'];
list($orig_w, $orig_h, $orig_type) = @getimagesize($file);
$image = wp_load_image($file);
imagefilter($image, IMG_FILTER_GRAYSCALE);
switch ($orig_type) {
case IMAGETYPE_GIF:
imagegif( $image, $file );
break;
case IMAGETYPE_PNG:
imagepng( $image, $file );
break;
case IMAGETYPE_JPEG:
imagejpeg( $image, $file );
break;
}
return $meta;
}

add_filter('wp_generate_attachment_metadata','bw_filter');


Warning: imagefilter() expects parameter 1 to be resource, string given

But I’m getting it because the Page that I’m uploading the image to was published last month, and wp_upload_dir() returns the current month’s upload path, so it looks like the image doesn’t exist.

Any suggestions on how I might go about fixing this? I’d love to be able to generate b/w thumbs for both posts and pages, regardless of when they were published.

Thanks!