<story><title>Show HN: Detect upsampling in images</title><url>https://github.com/0x09/resdet</url></story><parent_chain></parent_chain><comment><author>stevetjoa</author><text>For anyone interested in this area, the IEEE Transactions on Information Forensics and Security (TIFS) [1] is full of papers on the so-called area of &lt;i&gt;image forensics&lt;/i&gt; -- the identification of processing that has been performed upon an image, including resampling, rotation, JPEG compression, block processing, and more.&lt;p&gt;Consequently, another hot research area is &lt;i&gt;image anti-forensics&lt;/i&gt; -- the obfuscation of such operations to avoid detection. (Shameless self-promotion: one example paper on anti-forensics of JPEG compression can be found here [2].)&lt;p&gt;[1] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.signalprocessingsociety.org&amp;#x2F;publications&amp;#x2F;periodicals&amp;#x2F;forensics&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.signalprocessingsociety.org&amp;#x2F;publications&amp;#x2F;periodic...&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.mirlab.org&amp;#x2F;conference_papers&amp;#x2F;International_Conference&amp;#x2F;ICASSP%202010&amp;#x2F;pdfs&amp;#x2F;0001694.pdf&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.mirlab.org&amp;#x2F;conference_papers&amp;#x2F;International_Confer...&lt;/a&gt;</text></comment>
<story><title>Show HN: Detect upsampling in images</title><url>https://github.com/0x09/resdet</url></story><parent_chain></parent_chain><comment><author>mozumder</author><text>You can detect downsampling by looking at chroma frequencies.  Bayer pattern color filters on cameras mean that color resolution is never going to be as high as pixel resolution (assuming 1:1 mapping of pixels to sensor pixels) and if you see chroma frequencies that are higher than 2x pixel densities, then you have some downsampling going on.</text></comment>