Getting arty

The imagefilledrectangle() function takes six parameters in total, which are, in order: an image resource to draw on, the top-left X coordinate, the top-left Y coordinate, the bottom-right X coordinate, the bottom-right Y coordinate, and a colour to use. Note that there is a similar function called imagerectangle(), which takes exactly the same parameters with the difference being that it only draws the outline of the rectangle, whereas imagefilledrectangle() fills the shape in with colour.

In order to draw a rectangle in such a way as to make it stand out, we need to allocate another colour, then draw the rectangle. Here is how that is done:

$white = imagecolorallocate($image, 255, 255, 255);
imagefilledrectangle($image, 10, 10, 390, 290, $white);

Put those two lines just after the definition of $gold, then save the modified script and refresh phppicture.html. Not surprisingly, we now have a rectangle in there.

In case you are getting bored with simple stuff, let's take a leap forward with imagefilledrectangle() and draw a pattern using a loop. Take a copy of picture1.php and call it picture2.php - be sure to modify your HTML so that the image SRC points to picture2.php.

Bring up picture2.php in your favourite editor, and modify it to this:

<?php
    $image = imagecreate(400,300);
    $gold = imagecolorallocate($image, 255, 240, 00);
    $white = imagecolorallocate($image, 255, 255, 255);
    $colour = $white;

    for ($i = 400, $j = 300; $i > 0; $i -= 4, $j -= 3) {
        if ($colour == $white) {
            $colour = $gold;
        } else {
            $colour = $white;
        }

        imagefilledrectangle($image, 400 - $i, 300 - $j, $i, $j, $colour);
    }

    imagepng($image);
    imagedestroy($image);
?>

The code is pretty much the same as before, with the addition of a simple for loop. Note that our loop sets the starting value for $i and $j, and also decrements $i and $j with each iteration.

As you can see in the code, we call imagefilledrectangle() each iteration of the loop, slowly making the rectangle smaller and smaller as $i and $j decrease in value. Save the script, and see how it looks in your web browser.

Copyright ©2015 Paul Hudson. Follow me: @twostraws.