svg – Blur Filters: Box Blur

<svg width="900px" height="400px" viewBox="900 400">
   <defs>
      <filter id="GaussianHardEdge" >
         <feConvolveMatrix order="3" kernelMatrix=" 1 1 1
                                                    1 1 1
                                                    1 1 1"/>
      </filter>
   </defs>
        
   <image xlink:href="https://upload.wikimedia.org/wikipedia/commons/a/af/Fruit_Stall_in_Barcelona_Market.jpg" x="20px" y="20px" width="300px" height="200px" preserveAspectRatio="xMinYMin meet" />
   <image filter="url(#GaussianHardEdge)" xlink:href="https://upload.wikimedia.org/wikipedia/commons/a/af/Fruit_Stall_in_Barcelona_Market.jpg" x="340px" y="20px" width="300px" height="200px" preserveAspectRatio="xMinYMin meet"/>
</svg>

enter image description here

(Source image by Daderot at Wikimedia Commons)

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svg – Blur Filters: Box Blur - CodeDay