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Resizing QRCode from base64 png in PHP – Photoshop

I get a QRCode png as base64 from a remote service and need to display it on the web. When blowing the picture up without the “vector” data, it blurs:

enter image description here

I write the base64 to disk with 

fwrite($ifp, base64_decode($this->getQRCode()));

The resulting png is a bit small (29×29 pixels). When I open it with e.g. Photoshop, I can blow it up without loss so it looks like the “vector” data is intact. Note the “pixels”:

enter image description here

How can I do this on the server side before writing it down to disk and linking to it from the web.

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2

Answers


  1. Chosen as BEST ANSWER
    0

    The old school way of blowing up images was to (ideally) double pixels. Smoothing the rough edges that were the result of that process was invented later. So now I go with this:

    imagescale($image, 128, 128, IMG_NEAREST_NEIGHBOUR);

  2. 0

    You don’t say how you are “blowing the picture up.” Have you tried rescaling the image in PHP?

    $image = imagecreatefrompng($filename);
$bigimage = imagescale($image, 128, 128, IMG_NEAREST_NEIGHBOUR);
header("Content-Type: image/png");
//dumps directly to output
imagepng($bigimage, null, 0);

    Edit: you can try various interpolation modes as specified here, if IMG_NEAREST_NEIGHBOUR isn’t suitable. (Also, note the British/Canadian spelling of neighbour.)

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