<story><title>Magic PNG Thumbnails</title><url>http://thume.ca/projects/2012/11/14/magic-png-files/</url></story><parent_chain><item><author>pygy_</author><text>Could someone explain why this image is flickering on my MacBook Air screen?&lt;p&gt;&lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;thume.ca&amp;#x2F;assets&amp;#x2F;postassets&amp;#x2F;doubleVision&amp;#x2F;out.png&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;thume.ca&amp;#x2F;assets&amp;#x2F;postassets&amp;#x2F;doubleVision&amp;#x2F;out.png&lt;/a&gt;&lt;p&gt;Especially &amp;quot;ze first&amp;quot; image as seen in FF and Chrome.&lt;p&gt;I suppose it is related to how monitors use temporal dithering to fake 24 bit colors when they really have 18 bits per pixel, but why is it more apparent on this kind of picture?&lt;p&gt;Is it a perceptual issue or a technical one?&lt;p&gt;It is also apparent when using Windows XP under virtualization. Some windows have checkerboard patterns that flicker.</text></item></parent_chain><comment><author>sp332</author><text>Here&amp;#x27;s a page with a test and a potential explanation &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.lagom.nl&amp;#x2F;lcd-test&amp;#x2F;inversion.php&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.lagom.nl&amp;#x2F;lcd-test&amp;#x2F;inversion.php&lt;/a&gt;</text></comment>
<story><title>Magic PNG Thumbnails</title><url>http://thume.ca/projects/2012/11/14/magic-png-files/</url></story><parent_chain><item><author>pygy_</author><text>Could someone explain why this image is flickering on my MacBook Air screen?&lt;p&gt;&lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;thume.ca&amp;#x2F;assets&amp;#x2F;postassets&amp;#x2F;doubleVision&amp;#x2F;out.png&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;thume.ca&amp;#x2F;assets&amp;#x2F;postassets&amp;#x2F;doubleVision&amp;#x2F;out.png&lt;/a&gt;&lt;p&gt;Especially &amp;quot;ze first&amp;quot; image as seen in FF and Chrome.&lt;p&gt;I suppose it is related to how monitors use temporal dithering to fake 24 bit colors when they really have 18 bits per pixel, but why is it more apparent on this kind of picture?&lt;p&gt;Is it a perceptual issue or a technical one?&lt;p&gt;It is also apparent when using Windows XP under virtualization. Some windows have checkerboard patterns that flicker.</text></item></parent_chain><comment><author>trishume</author><text>Yah this happens because the image is based on a grid. You can see it on any monitor if you open it up in an image viewer and zoom in an out.&lt;p&gt;As another commenter mentioned these effects are called Moiré patterns: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Moir%C3%A9_pattern&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Moir%C3%A9_pattern&lt;/a&gt;&lt;p&gt;They may be more or less apparent depending on the scaling on the image and the scaling algorithm being applied. Some scaling algorithms apply filters that can make the effect even &lt;i&gt;more&lt;/i&gt; weird than normal.</text></comment>