Submitting a Form Using an Image Tag

We actually jumped ahead in the code in order to explain what this application needed to accomplish and how it would go about it. Now let's look at it in order of execution.

//load the background image

$im = imagecreatefrompng("images/confirm.png");

$textColor = imagecolorallocate($im,255,255,255);//allocate white

//get text dimensions

$nameArr = handleName($fontSize,$fontPath,$im,$str);

$vPos = getVerticalPosition($im);//get vertical coordinate for all text

for($i = 0;$i < count($nameArr);$i++)

{

       imagettftext($im,$fontSize,0,$nameArr[$i]->hpos,$vPos,

       $textColor,$fontPath,$nameArr[$i]->textStr);

       $vPos = $vPos + $nameArr[$i]->h;

}

header("Content-type: image/png");

imagepng($im);

imagedestroy($im);

Once we have all the coordinates needed to place the text, it's time to actually write it to the image. The imagettftext function is used for each text box. Arguments are as mentioned before: image resource, the font size, the angle, the horizontal coordinate, the vertical position, the text color that we allocated, the font and the text string. Notice that at the end of each loop iteration, the height of the current text block is added to the vertical position. This will put the next text block below the previous.

Once all the text is placed, the HTTP header is sent, announcing that we are sending an image of type png. The imagepng() function then sends the image, and we use imagedestroy() to close the stream.

Conclusion

As you can see, the hardest part of all this was working with the text, and this example does not show what to do with the email address or entering the user in the contest, as your use of this form submission technique will depend on the situation. How the server side code works will vary depending on what platform you are using.

You now have an understanding of how an image tag can be used to submit a form and create a better user experience for the visitors of your site. For more information on GD and PHP, take a look at the PHP documentation at php.net.