PHP Image quality issue when rotating and merging

Question

When I combine two images as one background and the other as the target image. I am using png. When I rotate the target image and then merge, everything is fine, except that the edges of the rotated image become zigzags, which means they are not smooth. How to make edges smooth using php GD ???

The code I'm using is:

<?php

// Create image instances

$dest = imagecreatefrompng('bg.png');
$src = imagecreatefrompng('text.png');
$width = imagesx($src);
$height = imagesy($src);
imageantialias($src, true);
$color = imagecolorallocatealpha($src, 0, 0, 0, 127);
$rotated = imagerotate($src, 40, $color);
imagesavealpha($rotated, true);

// $trans_colour = imagecolorallocatealpha($rotated, 0, 0, 0, 127);
// imagefill($rotated, 0, 0, $trans_colour);

imagepng($rotated, 'shahid.png');
$new_img = imagecreatefrompng('shahid.png?');
$width = imagesx($new_img);
$height = imagesy($new_img);

// imagecopymerge($dest, $new_img, 50, 50, 0, 0, $width+60, $height+60, 100);

imagecopymerge_alpha($dest, $new_img, 0, 20, 0, 0, $width, $height, 100);

// Output and free from memory

header('Content-Type: image/png');
imagepng($dest);
imagedestroy($dest);
imagedestroy($src);

function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct)
{
    if (!isset($pct)) {
        return false;
    }

    $pct/= 100;

    // Get image width and height

    $w = imagesx($src_im);
    $h = imagesy($src_im);

    // Turn alpha blending off

    imagealphablending($src_im, false);

    // Find the most opaque pixel in the image (the one with the smallest alpha value)

    $minalpha = 127;
    for ($x = 0; $x < $w; $x++)
    for ($y = 0; $y < $h; $y++) {
        $alpha = (imagecolorat($src_im, $x, $y) >> 24) & 0xFF;
        if ($alpha < $minalpha) {
            $minalpha = $alpha;
        }
    }

    // loop through image pixels and modify alpha for each

    for ($x = 0; $x < $w; $x++) {
        for ($y = 0; $y < $h; $y++) {

            // get current alpha value (represents the TANSPARENCY!)

            $colorxy = imagecolorat($src_im, $x, $y);
            $alpha = ($colorxy >> 24) & 0xFF;

            // calculate new alpha

            if ($minalpha !== 127) {
                $alpha = 127 + 127 * $pct * ($alpha - 127) / (127 - $minalpha);
            }
            else {
                $alpha+= 127 * $pct;
            }

            // get the color index with new alpha

            $alphacolorxy = imagecolorallocatealpha($src_im, ($colorxy >> 16) & 0xFF, ($colorxy >> 8) & 0xFF, $colorxy & 0xFF, $alpha);

            // set pixel with the new color + opacity

            if (!imagesetpixel($src_im, $x, $y, $alphacolorxy)) {
                return false;
            }
        }
    }

    // The image copy

    imagecopy($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h);
}

?>

Answer 1

I had this in an old project and worked for me. Anyway, I don’t remember if my png really had alpha transparency or "gif" transparency ...

$image = imagecreatefrompng($href);
$newImage = imagecreatefrompng($href2);
imagealphablending($image, true);
imagealphablending($newImage, true);
$newImage = imagerotate($newImage, $r, -1);
$blue = imagecolorallocate($newImage, 0, 0,255);
imagecolortransparent($newImage, $blue);
imagecopy($image,$newImage,$x,$y,0,0,imagesx($newImage) , imagesy($newImage));

From the manual in this case imagealphablendingshould be replaced byimagesavealpha