How to use imagescale and retain appearance of edge "pixels" - php

Question

So I have a 3x3 pixel image using imagecreate. I want to scale up the image with imagescale while maintaining the look of a 3x3 grid of "pixels". However, the pixels on the right and bottom edge are not the same size.
Here is my code and output image:
<?php
$image = imagecreate(3, 3);
imagecolorallocate($image, 0, 0, 255);
$red = imagecolorallocate($image, 255, 0, 0);
imagesetpixel($image, 0, 0, $red);
imagesetpixel($image, 1, 1, $red);
imagesetpixel($image, 2, 2, $red);
imagepng(imagescale($image, 200, 200, IMG_NEAREST_NEIGHBOUR));
header("Content-Type: image/png");
This is my output:
Notice how the bottom-right pixel is cut off. I kept playing with the numbers for the new dimensions and arrived at 256x256 at which point the pixels are all the same size.
This is the output after using 256x256:
My question is: How can I derive the dimensions to use for the resized image with the effect I described?
Bonus question: Is an alternative method which will allow me to resize to an arbitrary size and keep the pixels approximately the same size?

Answer 1

I would use imagecopyresampled to achieve this.
http://php.net/manual/en/function.imagecopyresampled.php
<?php
$width = 3;
$height = 3;
$image = imagecreate($width, $height);
imagecolorallocate($image, 0, 0, 255);
$red = imagecolorallocate($image, 255, 0, 0);
imagesetpixel($image, 0, 0, $red);
imagesetpixel($image, 1, 1, $red);
imagesetpixel($image, 2, 2, $red);
$new_width = 200;
$new_height = 200;
$dst = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($dst, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
imagepng($dst);
header("Content-Type: image/png");