Making image sharp with imagefilter() in php

Question

Is there any possibilities to make image more sharp using imagefilter() function? I am using imagettftext() which adds Anti-aliasing to fonts and the fonts looks bit de-focused. I like to make my final image bit sharpen so that I can reduce the blur around the char's in my image.

Different Test Images

Font used
- Roboto-Thin.ttf
- Roboto-Black.ttf

Image with light fonts

I like to have my fonts to look something like those lines next to it.

enter image description here

Image with dark fonts

enter image description here

Image with -$font_color (Some web resources suggested to make font colour value to negative which basically turns off the anti-aliasing) But in this case the fonts looks ugly. (Left-To-Right 100 is with turned off anti-aliasing)

enter image description here

I think you could achieve that by using `IMG_FILTER_CONTRAST`. Since that would make the black colors darker. For more about it, check here http://php.net/manual/en/function.imagefilter.php — Ignacio Belhot Colistro, Oct 25 '12 at 23:36

score 3 · Answer 1 · edited May 23 '17 at 11:48

There is no such filter in imagefilter() (you did try IMG_FILTER_EDGEDETECT? For sharp transitions maybe it can get you something). But you can try and use imageconvolution instead:

imageconvolution($imageResource, array(
    array( -1, -1, -1 ),
    array( -1, 16, -1 ),
    array( -1, -1, -1 ),
), 8, 0);

You may want to look at PHP imageconvolution() leaves black dot in the upper left corner , there appeared to be an issue with imageconvolution

Another possibility is to resize the image before applying text, making it (say) 200% larger. Then apply the text using a font again 200% larger. Then downsample the image. Depending on font characteristics, this will have the effect of reducing the blur. Using integer powers of 2 (200%, 400%, ...) helps reducing artifacts.

Baba · Accepted Answer · 2012-10-26T00:16:38.530

GD Solution

$old = "old.png";
$new = "new.png";

$im = imagecreatefrompng($imgname);
imagetruecolortopalette($im, FALSE, 256);
imagecolorset($im, imagecolorclosest($im, 159, 159, 159), 0, 0, 0);
imagecolorset($im, imagecolorclosest($im, 191, 191, 191), 0, 0, 0);

imagepng($im, $new);
imagedestroy($im);

Image Magic Solution

convert old.png -fuzz 0% -fill rgb(0,0,0) -opaque rgb(159,159,159) new.png
convert new.png -fuzz 0% -fill rgb(0,0,0) -opaque rgb(191,191,191) new.png

They would output

enter image description here

                  Old                           new

score 0 · Answer 3 · answered Oct 30 '12 at 21:36

You're using the two extremes of the Roboto font. Pick the light or Regular version and it will be dark without being too dark.

The anti-aliasing function of the font renderer can't make the thin lines less than one pixel thick, so it makes them dim instead.

Making image sharp with imagefilter() in php

Different Test Images

Image with light fonts

Image with dark fonts

Image with -$font_color (Some web resources suggested to make font colour value to negative which basically turns off the anti-aliasing) But in this case the fonts looks ugly. (Left-To-Right 100 is with turned off anti-aliasing)

3 Answers3