I am generating a website and my customer needs to puload multiple photos of each product.

I am using GD functions to make two copies of the photos. One a 640 x480 for a slide show and one 160 x 120 thumbnail for use on another page of the site.

The upload and the generation of the 640 x 480 version works great every time.

Generating the thumbnail works with most of the photos though sometimes refuses to work for some photos. If I upload 6 photos, 4 or 5 of them will be just fine but one or two MAY not work. For example:

product_1.jpg - works great
product_2.jpg - works great
product_3.jpg - works great
product_4.jpg - No thumbnail generated
product_5.jpg - works great
product_6.jpg - works great

In the above example, the photo named "product_4.jpg" did not work in the thumbnail generation but all others worked great. Changing the order of upload has no effect and "product_4.jpg" always fails the thumbnail generation. There is no real difference in file sizes so I can't see a problem there.

Any insight on what may be happening? I don't want to deliver a product that has random issues like this. Is there some other method besides imagecopyresized() I should use?

I don't have imagemajick on the web server at all and my hosting is ATT (used to be Yahoo).

Do not use GD to resize images, use imagemagick's convert utility.

If you do not have imagemagick on your host and there is no opportunity to install it there I strongly recommend you to change your hoster.

I think I solved, or worked around, the problem. It's all in the math! My original code:

PHP Code:

 function createthumb($name,$filename,$max_w,$max_h){
        $src_img=imagecreatefromjpeg("../images/".$name);

    $width=imageSX($src_img);
    $heigth=imageSY($src_img);

    $x_ratio= $max_w / $width;
    $y_ratio= $max_h / $heigth;

    if (($width <= $max_w) && ($heigth <= $max_h)){
        $tn_width = $width;
        $tn_heigth = $heigth;
    }
    else{
        $tn_width = ceil($x_ratio * $width);
        $tn_heigth = $max_h;
    }

    $dst_image = ImageCreateTrueColor($tn_width,$tn_heigth);
        imagecopyresampled($dst_image,$src_img,0,0,0,0,$tn_width,$tn_heigth,$width,$heigth);
    imagejpeg($dst_image,$filename,100);
    imagedestroy($src_img);
    imagedestroy($dst_image);
} 


This set the max heigth at a solid number no matter what the original image was. A simple change so to use the ratio for resize seems to have fixed it.

PHP Code:

$tn_heigth = ceil($y_ratio * $heigth); 


I had simply done a paste of a snippet to do this and now see that the original was flawed just slightly and that caused major confusion on my part.