How to rotate an image with a given angle using imagerotate() function in PHP?

The imagerotate() function is an inbuilt PHP function used to rotate an image by a specified angle in degrees. This function is part of the GD extension and provides a simple way to perform image rotation operations.

Note: This function requires the GD extension to be enabled. Install it using: sudo apt-get install php-gd (Ubuntu/Debian) or enable it in php.ini by uncommenting extension=gd.

Syntax

resource imagerotate($image, $angle, $bgd_color, $ignore_transparent = 0)

Parameters

The imagerotate() function accepts four parameters ?

• $image − An image resource created by functions like imagecreatetruecolor(), imagecreatefromjpeg(), etc.

• $angle − Rotation angle in degrees. Positive values rotate counterclockwise, negative values rotate clockwise.

• $bgd_color − Background color for uncovered areas after rotation. Use imagecolorallocate() to create the color.

• $ignore_transparent − Optional parameter. If non-zero, transparent colors are ignored (default is 0).

Return Value

Returns an image resource on success, or FALSE on failure.

Example 1: 90-Degree Rotation

<?php
    // Create a sample image
    $image = imagecreatefromjpeg('/path/to/your/image.jpg');
    
    // Create background color (black)
    $bgColor = imagecolorallocate($image, 0, 0, 0);
    
    // Rotate image 90 degrees counterclockwise
    $rotatedImage = imagerotate($image, 90, $bgColor);
    
    // Output image
    header("Content-type: image/jpeg");
    imagejpeg($rotatedImage);
    
    // Clean up memory
    imagedestroy($image);
    imagedestroy($rotatedImage);
?>

Example 2: 180-Degree Rotation

<?php
    // Load image
    $image = imagecreatefromjpeg('/path/to/your/image.jpg');
    
    // Create white background color
    $bgColor = imagecolorallocate($image, 255, 255, 255);
    
    // Rotate image 180 degrees
    $rotatedImage = imagerotate($image, 180, $bgColor);
    
    // Save to file instead of outputting
    imagejpeg($rotatedImage, '/path/to/output/rotated_image.jpg', 90);
    
    echo "Image rotated and saved successfully!";
    
    // Clean up
    imagedestroy($image);
    imagedestroy($rotatedImage);
?>

Example 3: Custom Angle with Transparent Background

<?php
    // Create a test image
    $image = imagecreatetruecolor(200, 200);
    $white = imagecolorallocate($image, 255, 255, 255);
    $black = imagecolorallocate($image, 0, 0, 0);
    
    // Draw a rectangle
    imagefill($image, 0, 0, $white);
    imagerectangle($image, 50, 50, 150, 150, $black);
    
    // Create transparent background for rotation
    $transparent = imagecolorallocatealpha($image, 0, 0, 0, 127);
    
    // Rotate 45 degrees
    $rotated = imagerotate($image, 45, $transparent);
    
    // Enable alpha blending
    imagealphablending($rotated, false);
    imagesavealpha($rotated, true);
    
    // Output as PNG to preserve transparency
    header("Content-type: image/png");
    imagepng($rotated);
    
    imagedestroy($image);
    imagedestroy($rotated);
?>

Key Points

• Positive angles rotate counterclockwise, negative angles rotate clockwise
• Use PNG format to preserve transparency in rotated images
• Always clean up image resources with imagedestroy() to free memory
• Background color fills the empty areas created during rotation

Conclusion

The imagerotate() function provides an efficient way to rotate images in PHP. Remember to handle transparency properly and always clean up image resources to prevent memory leaks.