To dynamically generate an image in GIF format should you notice?

If you use
int imagecreatefromgif (string filename);
To take a picture of a GIF format, when the background or basic canvas sample is used, draw a graphic on it, please note:
If there is no pigment in this file, you will not be able to use it.


Solution, you can use
int imagecreate (int x_size, int y_size);
Create a fully-empty graphic. Draw a graphic on it. Use black as a transparent color.
This new graphic will be the same size as the original graphic, absolute position is the same, put it above the original graphic, you can.

Original graphics file

Full-empty file photo.php

Code for photo.php:
<?php
Header ("Content-type:image/gif");
$im = Imagecreate (200,300);
$black = Imagecolorallocate ($im, 0,0,0);
$red = Imagecolorallocate ($im, 255,0,0);
$blue = Imagecolorallocate ($im, 0,0,255);

Imagerectangle ($im, 100,200,150,200, $red);
Imagestring ($im, 2,120,150, "aaaaaaaa", $blue);

Imagecolortransparent ($im, $black);
Use black as a transparent color

Imagegif ($im);
Imagedestroy ($im);

?>