imagefilledrectangle(): Draw Filled Rectangles in PHP GD

Example: Drawing a Filled Rectangle

<?php
header("Content-type: image/png");
$width = 300;
$height = 200;
$image = imagecreate($width, $height);

// Define colors
$background = imagecolorallocate($image, 255, 255, 255);
$fill_color = imagecolorallocate($image, 0, 102, 204); // Blue

imagefilledrectangle($image, 50, 50, 250, 150, $fill_color);

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

Syntax of imagefilledrectangle()

imagefilledrectangle($image, $x1, $y1, $x2, $y2, $color);

Example: Multiple Filled Rectangles

<?php
header("Content-type: image/png");
$width = 400;
$height = 300;
$image = imagecreate($width, $height);

// Define colors
$white = imagecolorallocate($image, 255, 255, 255);
$red = imagecolorallocate($image, 255, 0, 0);
$green = imagecolorallocate($image, 0, 255, 0);
$blue = imagecolorallocate($image, 0, 0, 255);

// Draw rectangles
imagefilledrectangle($image, 50, 50, 150, 150, $red);
imagefilledrectangle($image, 160, 50, 260, 150, $green);
imagefilledrectangle($image, 270, 50, 370, 150, $blue);

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

Creating Gradient Effect Using imagefilledrectangle()

A gradient effect can be achieved using imagefilledrectangle() by drawing multiple rectangles with slight color variations. This creates a smooth transition from one color to another.

Example: Vertical Gradient

<?php
header("Content-type: image/png");
$width = 300;
$height = 200;
$image = imagecreate($width, $height);

// Background color
$white = imagecolorallocate($image, 255, 255, 255);

// Loop to create gradient effect
for ($i = 0; $i < $height; $i++) {
    $color = imagecolorallocate($image,0,($i * 255 / $height),255);
    imagefilledrectangle($image, 0, $i, $width, $i + 1, $color);
}

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

Code Explanation

• Loops through each row of the image.
• Creates a color variation for each row.
• Applies filled rectangles for each row with progressively changing colors.
• Generates a gradient effect from cyan to blue .

Using imagefilledrectangle() to Highlight Text

We can use imagefilledrectangle() to create a highlight effect for text. This is useful for generating banners, notifications, or emphasized text elements in an image.

Example: Highlighted Text

<?php
header("Content-type: image/png");
$width = 400;
$height = 100;
$image = imagecreate($width, $height);

// Define colors
$white = imagecolorallocate($image, 255, 255, 255);
$highlight = imagecolorallocate($image, 255, 223, 186); // Light orange
$black = imagecolorallocate($image, 0, 0, 0);

// Draw highlight rectangle
imagefilledrectangle($image, 20, 30, 380, 70, $highlight);

// Add text over highlighted area
imagestring($image, 5, 40, 40, "Highlighted Text", $black);

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

Code Explanation

• Creates a background image using imagecreate().
• Defines a highlight color (light orange).
• Draws a rectangle behind the text using imagefilledrectangle().
• Adds text on top of the highlighted area using imagestring().
• Outputs the image as PNG for display.

Generating Multiple Rectangles with Common Center Using Random Colors

By using imagefilledrectangle(), we can draw multiple rectangles that share a common center while filling them with random colors. This technique creates a visually appealing effect with a nested rectangle pattern.

Example: Nested Rectangles with Random Colors

<?php
header("Content-type: image/jpeg");
$width = 600;
$height = 600;

$im = imagecreate($width, $height) 
    or die("Cannot Initialize new GD image stream");

$thickness = 10; // Gap between rectangles

// Loop to create multiple rectangles
for ($i = 0; $i <= $width / 2; $i += $thickness) {
    
    // Generate Random Colors
    $r = rand(1, 255);
    $g = rand(1, 255);
    $b = rand(1, 255);

    $box_color = imagecolorallocate($im, $r, $g, $b);

    // Draw rectangle with random color
    imagefilledrectangle($im, $i, $i, 
        $width - $i, $height - $i, $box_color);
}

// Output the image as JPEG
imagejpeg($im);
imagedestroy($im); // Free memory
?>

Code Explanation

• Creates an image canvas of 600x600 pixels.
• Defines a background color (white).
• Uses a loop to generate rectangles, shrinking each step.
• Generates random colors for each rectangle.
• Draws rectangles using imagefilledrectangle(), keeping a common center.
• Outputs the final image as a JPEG.

Output

By running this script, you will see multiple colorful rectangles, each smaller than the previous one, creating a nested effect with a common center.

This is a useful technique for creating geometric patterns dynamically in PHP!

Creating a Simple Bar Chart Using PHP GD Library imagefilledrectangle

<?php
// Set the image width and height
$width = 400;
$height = 300;
$image = imagecreate($width, $height);

// Define colors
$white = imagecolorallocate($image, 255, 255, 255); // Background color
$black = imagecolorallocate($image, 0, 0, 0);       // Axis and text color
$blue = imagecolorallocate($image, 0, 102, 204);    // Bar color

// Sample Data
$data = [50, 80, 120, 60, 90]; // Values for bars
$bar_width = 40;               // Width of each bar
$gap = 20;                     // Space between bars
$base = $height - 30;          // Base of bars

// Draw axes
imageline($image, 40, 10, 40, $base, $black); // Y-axis
imageline($image, 40, $base, $width - 10, $base, $black); // X-axis

// Draw bars
$x = 50; // Initial x position for first bar
foreach ($data as $value) {
    imagefilledrectangle($image, $x, $base - $value, $x + $bar_width, $base, $blue);
    imagestring($image, 4, $x + 10, $base - $value - 15, $value, $black);
    $x += $bar_width + $gap; // Move x position for next bar
}

// Output the image
header("Content-Type: image/png");
imagepng($image);
imagedestroy($image);
?>

• Image Creation: We create a blank image of 400x300 pixels using imagecreate().
• Color Allocation: The function imagecolorallocate() is used to define colors for:
  • White background
  • Black for axes and labels
  • Blue for the bars
• Drawing Axes:
  • The imageline() function is used to draw the X-axis and Y-axis.
  • The Y-axis starts at `(40,10)` and extends to `(40, base)`.
  • The X-axis extends from `(40, base)` to the right edge of the image.
• Drawing Bars:
  • A `foreach` loop iterates over the data values.
  • Each bar is drawn using imagefilledrectangle(), with the height corresponding to the value.
  • Text labels are placed above the bars using imagestring().
  • The `$x` position is incremented for the next bar.
• Outputting the Image:
  • header("Content-Type: image/png") ensures the image is displayed as a PNG.
  • imagepng() sends the image to the browser.
  • imagedestroy() clears memory after execution.

Including this graph in a web page

<img src="test1.php?time=<?php echo time(); ?>" alt="Dynamic Image">

Conclusion

The imagefilledrectangle() function is a useful tool for creating filled rectangles in PHP GD. It can be used for:

• Highlighting text in generated images
• Creating UI elements such as buttons and boxes
• Generating bar charts dynamically