Generate centered thumbnail from first frame of GIF with ImageMagick - php

Question

I have the following method to generate a thumbnail. It takes any dimensions and converts it to a 600 x 450 image, centered.
private function generateThumbnail ($ext, $name) {
if ($ext === ".png"){
exec('convert -define png:size=1200x900 '.$this->file.' -thumbnail 600x450^ -gravity center -extent 600x450 '.$name);
exec("optipng -o2 -q " . $name);
} else {
exec('convert -define jpeg:size=1200x900 '.$this->file.' -thumbnail 600x450^ -gravity center -extent 600x450 '.$name);
$img = new Imagick($name);
$img->setImageCompression(Imagick::COMPRESSION_JPEG);
$img->setImageCompressionQuality(97);
$img->stripImage();
$img->writeImage($name);
$img->destroy();
}
}
The problem arises when generating a thumbnail from a GIF. It doesn't generate an image from the first frame. One GIF just had a blank image (transparent), another had strange colors/quality.
How do I generate a thumbnail the first frame of a GIF, centered?

Answer 1

You could probably do them with the API but I do not use it as it is limited. But it looks like you still need to use the command line for the optipng program anyway so I would have carried on with the command line.
Anyway back to your problem; how do you know the first frames of the gif are not a transparent image or a strange image?
As #Mark Setchell said you should be able to specify a specific frame with input.gif[0] and I would try that with a different number and see what you get.
I am not an animation use but you should be able to see the gif frames with -coalesce. Anthony has some examples on his site: http://www.imagemagick.org/Usage/anim_basics/#coalesce
This should give you an idea of the frames in the gif:
montage script_k.gif -coalesce \
-tile x1 -frame 4 -geometry '+2+2' \
-background none -bordercolor none coalesce_k_montage.gif
You can see how you gif file is made and perhaps go for the second or third frame rather than the first.