PHP compress/reduce blob image data size

Question

I'm trying to reduce an images blob size to under 150 KB

I've made a php function to do this however imagejpeg keeps on outputing data instead of storing it into a variable.

Basically, does anybody know how to compress an image into 150KB or lower? Quality loss is okay.

It comes in as base64. Then I decode it to a blob and pass it through this function.

function compressImageBlob($image_blob, $type, $loop = 0) {

    global $MAX_IMAGE_SIZE;

    $blob_size = strlen($image_blob);
    $loop++;

    if($loop > 10){
        return $image_blob;
    }

    if($blob_size >= $MAX_IMAGE_SIZE){
        $quality = ($MAX_IMAGE_SIZE/$blob_size)*10;

        if($quality >= 100){
            // it should never come here, but just in case
            $quality = 10;
        }

        $img = imagecreatefromstring($image_blob);
        $image_blob = imagejpeg($img, NULL, $quality);
        $image_blob = compressImageBlob($image_blob,$type,$loop);
    }

  return $image_blob;
}

Mark Setchell · Accepted Answer · 2018-06-10 09:16:49Z

2

I can't tell if your issue is creating a blob instead of a file, or how to compress. I assume it is the former. I think you need to do the following to create a blob rather than a file:

ob_start();                      // Start output buffering
imagejpeg($img,NULL,$quality);   // Generate JPEG into buffer
$blob=ob_get_contents();         // Load output buffer into $blob var
ob_end_clean();                  // Clean up buffer

In case you are unfamiliar, it is called "output buffering" and there's an example here.

edited Jun 10, 2018 at 9:16

answered Jun 10, 2018 at 9:05

Mark Setchell

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2 Comments

Trevor Over a year ago

thanks for the response. I'm able to create a blob and pass it to the function. However whenever I call imagejpeg. It directly prints the blob to the screen instead of storing it in the variable

Trevor Over a year ago

ah! Just read about object buffering. This may be my problem.

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