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POHow does WinRT handle BitmapImage and Image memory
 

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  1. POHow does WinRT handle BitmapImage and Image memory
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    <p>I am new to programming <strong>Windows</strong> Store Apps with <code>C#</code> and I am trying to understand how image memory is handled. My app is very simple:</p> <p>1) it references a bitmap from a file using a <code>Windows.UI.Xaml.Media.Imaging.BitmapImage</code> object and then uses that as the Source for a <code>Windows.UI.Xaml.Controls.Image</code> object. In my case the image on disk has larger dimensions than what is being displayed on screen so it is being scaled by the system.</p> <p>My question is how does <strong>WinRT</strong> handle the memory for the image? I used the <em><code>vmmap</code></em> tool and I see in the Mapped File section there is an entry for my image file. I guess this means that the raw bytes for this file are fully loaded into memory. Since this is a JPG these bytes must be decoded into pixel bytes. It seems from my tests that setting the UriSource of the BitmapImage doesn't actually cause any processing to take place since it takes 0 ms and that instead there is some lazy loading going on.</p> <p>So the questions are: Which object is dominator of the the uncompressed unscaled pixel data? What object is the dominator for the scaled pixel data that gets drawn on screen? Are there tools that can easily show me this? In the Java world I use the Eclipse memory analyzer tool. I tried using PerfView but the results make no sense to me, it seems the tool was meant for analyzing performance.</p> <p><strong>UPDATE</strong>:</p> <p>At the BUILD conference the team discussed the <code>Windows Performance Toolkit</code>. I never heard anyone mention PerfView so I believe that WPT is the latest and greatest tool for analyzing memory and performance, here is a link:</p> <p><a href="http://msdn.microsoft.com/en-us/performance/cc825801.aspx">http://msdn.microsoft.com/en-us/performance/cc825801.aspx</a></p>
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    1. COThere's a pretty steep api behind this, start reading [here](http://msdn.microsoft.com/en-us/library/windows/desktop/ee719902%28v=vs.85%29.aspx)
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      1. USHans Passant
    2. COI believe most image source objects are backed behind an InMemoryRandomAccessStream or something similar. You can attempt to use PerfView/PerfMon to try and find out a bit more though.
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      1. USNate Diamond
    3. COI don't remember exactly but doesn't the Image control scale the source based on its size settings? I.E. You are putting a control in a xaml window and the framework element that is the image control is sized at say 800x600 when the image is really 1920x1080?
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      1. USPaul Wade
 

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