Things to note when dynamically generating images in gif format

If you use
int imagecreatefromgif(string filename);
To take out a GIF format graphic and use it as a background or basic canvas sample to draw graphics 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 completely empty graph. Draw graphics on it. Use black as the transparent color.
The newly created graphic should be the same size and absolute position as the original graphic. Just place it above the original graphic.


Original graphic file


Completely empty file photo.php

Code for photo.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 transparent color

ImageGif($im);
ImageDestroy($im);

?>

The above introduces the precautions for dynamically generating images in GIF format, including the content of dynamically generating GIFs. I hope it will be helpful to friends who are interested in PHP tutorials.