Question

I’m trying to build a function that takes a PHP image resource and places it in the center of a new image of predetermined size. I do not want to scale the image; rather I want to place it as-is in the center of an enlarged “canvas.”

$img is a valid image resource – if I return it I receive the correct original (unprocessed) image. $canvas_w and $canvas_h are the width and height of the desired new canvas. It’s creating the correct size canvas, but the contents of the file are unexpectedly solid black when I return the desired “corrected” image resource ($newimg).

// what file?
$file = 'smile.jpg';

// load the image
$img = imagecreatefromjpeg($file);

// resize canvas (not the source data)
$newimg = imageCorrect($img, false, 1024, 768);

// insert image
header("Content-Type: image/jpeg");
imagejpeg($newimg);
exit;

function imageCorrect($image, $background = false, $canvas_w, $canvas_h) {
    if (!$background) {
        $background = imagecolorallocate($image, 255, 255, 255);
    }
    $img_h = imagesy($image);
    $img_w = imagesx($image);

    // create new image (canvas) of proper aspect ratio
    $img = imagecreatetruecolor($canvas_w, $canvas_h);

    // fill the background
    imagefill($img, 0, 0, $background);

    // offset values (center the original image to new canvas)
    $xoffset = ($canvas_w - $img_w) / 2;
    $yoffset = ($canvas_h - $img_h) / 2;

    // copy
    imagecopy($img, $image, $xoffset, $yoffset, $canvas_w, $canvas_h, $img_w, $img_h);

    // destroy old image cursor
    //imagedestroy($image);
    return $img; // returns a black original file area properly sized/filled
    //return $image; // works to return the unprocessed file
}

Any hints or obvious errors here? Thanks for any suggestions.

Answer 1

In place of imagecopy(), this seemed to work:

imagecopymerge($img, $image, $xoffset, $yoffset, 0,0, $img_w, $img_h, 100);