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/**
 * Scale an image according to input canvas dimensions. 
 * No cropping will occur, the scaled image is "centered" to canvas.
 */

function imageToCanvas ($_image, $_canvasWidth, $_canvasHeight)
{
    if (is_string($_image)) {
        if (is_file($_image)) {
            $_image = imagecreatefromjpeg($_image);
        } else {
            return "Incorrect imagepath >> No file here " . $_image;
        }
    } 
    
    $width = imagesx($_image);
    $height = imagesy($_image);
    $image_aspect_ratio = $width / $height;
    $canvas_aspect_ratio = $_canvasWidth / $_canvasHeight;
    
    // scale by height
    if ($image_aspect_ratio < $canvas_aspect_ratio) {
        $new_height = $_canvasHeight;
        $new_width = ($new_height/$height) * $width;
    } 
    // scale by width
    else {
        $new_width = $_canvasWidth;
        $new_height = ($new_width/$width) * $height;
    }
    
    # offset values (ie. center the resized image to canvas)
    $xoffset = ($_canvasWidth - $new_width) / 2;
    $yoffset = ($_canvasHeight - $new_height) / 2;
    
    $image_resized = imagecreatetruecolor($_canvasWidth, $_canvasHeight);
    
    # fill colour
    $white = imagecolorallocate($image_resized, 255, 255, 255);
    imagefill($image_resized, 0, 0, $white);
    imagecopyresampled($image_resized, $_image, $xoffset, $yoffset, 0, 0, $new_width, $new_height, $width, $height);
    
    imagedestroy($_image);
    return $image_resized;
}