test image generation (NG)

testimageNG.php

<?php

function cramp255($v) {
    if ($v < 0) {
        return 0;
    }
    return ($v<=255)?$v:255;
}

function getRGBA($x, $y, $width, $height) {
    $divX = 3000; $divY = 3000;
    $xRatio = $x / $width;
    $yRatio = $y / $height;
    $xx = $xRatio - 0.5;
    $yy = $yRatio - 0.5;
    $dRatio = sqrt($xx * $xx * $divX + $yy * $yy * $divY);
    $l = sin($dRatio * 2 * M_PI);
    $r = 255 * $l;
    $g = 255 * sin($xRatio * 2 * M_PI * 4) * $l;
    $b = 255 * sin($yRatio * 2 * M_PI * 4) * $l;
    $a = 0;
    return [cramp255($r), cramp255($g), cramp255($b), cramp255($a)];
}

if ($argc < 3) {
    echo "Usage: php testimageNG.php <width> <height>".PHP_EOL;
    echo "ex) php testimageNG.php 320 320".PHP_EOL;
    exit (1);
}

list($prog, $width, $height) = $argv;

$im = imagecreatetruecolor($width, $height);
for ($y = 0 ; $y < $height ; $y++) {
    for ($x = 0 ; $x < $width ; $x++) {
        list($r, $g, $b, $a) = getRGBA($x, $y, $width, $height);
        $c = imagecolorallocatealpha($im, $r, $g, $b, $a);
        imagesetpixel($im, $x, $y, $c);
    }
}
// imagesavealpha($im, true);
imagepng($im);