1. Better antialiasing with GD based on resampling
GD has shitty antialiasing implementation, but this can be quickly fixed with a simple hack:
<?php
$im = imagecreatetruecolor(4000, 3000);
imageantialias($im, true);
$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);
imagefilledellipse($im, 2000, 1500, 800, 800, $c_green);
$imf = imagecreatetruecolor(400, 300);
imagecopyresampled($imf, $im, 0,0,0,0, 400,300,4000,3000);
imagePng($imf, '/tmp/image.png');
-
4000, 3000- we have created initial image of large size (10x what we need in result), -
imagecopyresampled- now we resize source large image (4000x3000) to resulting image (400x300) to apply better antialiasing.
Open original or edit on Github.
2. Resize an image proportionally
<?php
$file = '/var/www/examples/heroine.png';
$size = getimagesize($file);
$im = imagecreatefrompng($file);
$w = 400;
$h = $w * $size[1] / $size[0];
$imf = imagecreatetruecolor($w, $h);
imagecopyresampled($imf, $im, 0,0,0,0, $w,$h,$size[0],$size[1]);
imagePng($imf, '/tmp/image.png');
-
$w = 400- resize image to 400 pixels wide, -
$w * $size[1] / $size[0]- calculates resized image height based on source image proportions.
Open original or edit on Github.
3. Resize transparent PNG image
<?php
$file = '/var/www/examples/clouds.png';
$size = getimagesize($file);
$im = imagecreatefrompng($file);
$w = 300;
$h = $w * $size[1] / $size[0];
$imf = imagecreatetruecolor($w, $h);
imagealphablending($imf, false);
imagesavealpha($imf, true);
imagecopyresampled($imf, $im, 0,0,0,0, $w,$h,$size[0],$size[1]);
imagePng($imf, '/tmp/image.png');
-
imagealphablending- we're disabling alpha blending to prevent transparent background being converted to black color, -
imagesavealpha- we're enabling alpha channel (controls transparency) for resulting image.
Top comments (0)