im taking image uploads on a website and changing the images to thumbnails that fit onto a 100 x 100 white square. the problem is that the images look like they dont anti-alias properly. images sized down in photoshop look smooth, but these look crunchy, like super sharpened.
take a look at these samples , showing full size on the left and thumbnails on the right (view at 100%). the photo comes out looking ridiculously sharpened, but a lot of people might not be bothered by it. the drawing though is waaay unacceptable. those curved lines just dont anti-alias at all and become dotted lines.
im using imagejpg(), and the jpg quality i choose has no effect on the crunchiness. heres some of the code surrounding it:
$tmp_img = imagecreatetruecolor( $maxSize, $maxSize );
$white = ImageColorAllocate ($tmp_img, 255, 255, 255);
ImageFill($tmp_img, 0, 0, $white);
imagecopyresized( $tmp_img, $img, $offsetx, $offsety, 0, 0, $new_width, $new_height, $width, $height );
$thumbFullPath = "{$pathToThumbs}/{$filenameNoExtension}.jpg";
imagejpeg( $tmp_img, $thumbFullPath, 90 );
any ideas? is this normal? thanks!
You may want to try imagecopyresampled
instead of imagecopyresized
. It's slower but uses a more sophisticated algorithm for determining the colour of every pixel in the new image.
change the last line to:
imagejpeg( $tmp_img, $thumbFullPath, 100 );
see: http://us4.php.net/manual/en/function.imagejpeg.php
Also, try using imagecopyresampled()
rather than imagecopyresized()
see: http://us4.php.net/manual/en/function.imagecopyresampled.php
$imagepath = /path/to/image.jpg;
$image = imagecreatefromjpeg($imagepath);
header('Content-Type: image/jpeg');
imagejpeg($image, NULL, 100);
Last line is so important!
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