Can't find the bug

[Bah__Name]

I've got this function that flips an image from left to right, but it only works on some of my images, on others, it has a little problem on the far right of the flipped image, and I can't seem to find why.

function FlipImage( $image, $imagestr ) {
 $image_info = GetImageSize( $imagestr );
 list($image_width, $image_height, $image_type, $image_width_height_string) = $image_info;
 $imageTemp = ImageCreate(1,$image_height);
 $j=$image_width-1;
 for ($i=0; $i<($image_width/2)-1; $i++){
  ImageCopy( $imageTemp, $image,  0,0, $i,0, 1,$image_height);
  ImageCopy( $image,     $image, $i,0, $j,0, 1,$image_height);
  ImageCopy( $image, $imageTemp, $j,0,  0,0, 1,$image_height);
  $j-=1;
 }ImageDestroy( $imageTemp );}

[khurramijaz]

See where width is divided by 2 . if the width is 21 the loop will run 10 times. so 1 pixel width line will be lost. If that does not work do ask again.

[Bah__Name]

I've tried that, now hasn't made a difference. All my files are an odd number long incidentally(!), and some are okay. If I fiddle, they are thrown out.