How to retain exact Product Image Quality

Question

I have modified view.xml to increase the Large image dimensions.

<image id="product_page_image_large" type="image"/>
        <image id="product_page_image_medium" type="image">
            <width>864</width>
            <height>864</height>
        </image>

So, my original product image & Lightbox Large Image have same dimensions. However, there is visible degrading in quality of image. If I remove the cache/hash.. & view/compare the uploaded image, the image appears degraded.

So, it appears file upload is processing my image even though it doesnt need to do anything, as dimensions are within limits.

Additionally, I have switched from GD to IMAGICK.

And via AminPanel I have set JPG quality to 100% & disabled Javascript Image processing while file upload.

Pl. help me understand how to stop Magento from re-processing my product images(large). I want it to take the image, as is.(if it fits within its dimension limit)