How to draw a slightly diagonal gradient Fill in PHP?

Question

I found that the following function can draw a vertical gradient in PHP. However, many web designers, like their gradients, have an upper left light source to make the gradient more realistic. So, how do you slightly change the angle on a vertical gradient, turning it into a small gradient? I do not want to overdo it completely, but only a slight movement to the right when it is moving along a vertical gradient.

<?php

function hex2rgb($sColor) {
    $sColor = str_replace('#','',$sColor);
    $nLen = strlen($sColor) / 3;
    $anRGB = array();
    $anRGB[]=hexdec(str_repeat(substr($sColor,0,$nLen),2/$nLen));
    $anRGB[]=hexdec(str_repeat(substr($sColor,$nLen,$nLen),2/$nLen));
    $anRGB[]=hexdec(str_repeat(substr($sColor,2*$nLen,$nLen),2/$nLen));
    return $anRGB;
}

$nWidth = 960;
$nHeight = 250;
$sStartColor = '#2b8ae1';
$sEndColor = '#0054a1';
$nStep = 1;

$hImage = imagecreatetruecolor($nWidth,$nHeight);
$nRows = imagesy($hImage);
$nCols = imagesx($hImage);
list($r1,$g1,$b1) = hex2rgb($sStartColor);
list($r2,$g2,$b2) = hex2rgb($sEndColor);
$nOld_r = 0; $nOld_g = 0; $nOld_b = 0;
for ( $i = 0; $i < $nRows; $i=$i+1+$nStep ) {
    $r = ( $r2 - $r1 != 0 ) ? intval( $r1 + ( $r2 - $r1 ) * ( $i / $nRows ) ): $r1;
    $g = ( $g2 - $g1 != 0 ) ? intval( $g1 + ( $g2 - $g1 ) * ( $i / $nRows ) ): $g1;
    $b = ( $b2 - $b1 != 0 ) ? intval( $b1 + ( $b2 - $b1 ) * ( $i / $nRows ) ): $b1;
    if ( "$nOld_r,$nOld_g,$nOld_b" != "$r,$g,$b") {
        $hFill = imagecolorallocate( $hImage, $r, $g, $b );
    }
    imagefilledrectangle($hImage, 0, $i, $nCols, $i+$nStep, $hFill);
    $nOld_r= $r;
    $nOld_g= $g;
    $nOld_b= $b;
}
header("Content-type: image/png");
imagepng($hImage);

Answer 1

The following snippet works much faster than the GD libraries and without complexity. However, you need to install the ImageMagick extension for PHP.

$oImage = new Imagick();
$oImage->newPseudoImage(1000, 400, 'gradient:#09F-#048' );
$oImage->rotateImage(new ImagickPixel(), -3);
$oImage->cropImage(960, 250, 25, 100);
$oImage->setImageFormat('png');
header( "Content-Type: image/png" );
echo $oImage;

Answer 2

, , :

...
$degrees = -5;
$newImage = imagecreatetruecolor($nWidth, $nHeight);
$rotated = imagerotate($hImage, $degrees, 0);
imagecopy($newImage, $rotated, 0, 0, $x, $y, $width, $height)