Encoding problem? Replacement char appearing, can't get image encoded

[Theo4]

trafficstars

Hello,

I tried to test this source to get a properly encoded bitmap image and it looks like something is wrong

getRasterFormatFromFile() return this : https://i.postimg.cc/zB3Mpfxr/caption.png ( simply via the code below : $this -> imgRasterData = $this->getRasterFormatFromFile($this->filename); echo $this->imgRasterData; )

It is also the same without allowOptimisations.

Am I doing something wrong with encoding or anything like this?

Thank you for your help!