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	<title>Comments on: Image overlays</title>
	<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/</link>
	<description>Steve Eddins manages the Image &#38; Geospatial development team at &#60;a href="http://www.mathworks.com/"&#62;The MathWorks&#60;/a&#62; and coauthored &#60;a href="http://www.mathworks.com/support/books/book5291.html?category=-1&#38;language=-1"&#62;Digital Image Processing Using MATLAB&#60;/a&#62;. He writes here about image processing concepts, algorithm implementations, and MATLAB.&#60;br&#62;&#60;br&#62;&#60;img&#62;</description>
	<pubDate>Sun, 08 Nov 2009 05:24:55 +0000</pubDate>
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		<title>By: Robbe</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22243</link>
		<dc:creator>Robbe</dc:creator>
		<pubDate>Tue, 20 Oct 2009 14:29:03 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22243</guid>
		<description>Thanks Steve !! it worked perfectly</description>
		<content:encoded><![CDATA[<p>Thanks Steve !! it worked perfectly</p>
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		<title>By: Steve</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22242</link>
		<dc:creator>Steve</dc:creator>
		<pubDate>Tue, 20 Oct 2009 12:21:42 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22242</guid>
		<description>Robbe&#8212;Dilate the mask:

&lt;pre&gt;
thicker_mask = imdilate(mask, ones(3, 3));
&lt;/pre&gt;</description>
		<content:encoded><![CDATA[<p>Robbe&mdash;Dilate the mask:</p>
<pre>
thicker_mask = imdilate(mask, ones(3, 3));
</pre>
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		<title>By: Robbe</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22241</link>
		<dc:creator>Robbe</dc:creator>
		<pubDate>Tue, 20 Oct 2009 12:19:32 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-22241</guid>
		<description>Hi Steve,

Can you please tell me how can I make imoverlay output line thicker?</description>
		<content:encoded><![CDATA[<p>Hi Steve,</p>
<p>Can you please tell me how can I make imoverlay output line thicker?</p>
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		<title>By: Steve</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21966</link>
		<dc:creator>Steve</dc:creator>
		<pubDate>Mon, 13 Jul 2009 12:59:08 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21966</guid>
		<description>Chuck&#8212;My overlay code here produces a "truecolor" image, which is an M-by-N-by-3 array.  The first plane is the red component, the second plane is the green component, and the third plane is the blue component.  The color of each image pixel is determined directly from these values, rather than indirectly via the figure colormap.  Unfortunately, this means that colorbar doesn't work directly with such images.

So you need to do little extra work.  One approach is to display the image as you already do, using &lt;tt&gt;imagesc&lt;/tt&gt; and the desired colormap.  Call &lt;tt&gt;imagesc&lt;/tt&gt; with an output argument so you can save the handle to the created image object.  Then call colorbar.  Finally, set the CData of the image object to the overlay image created using the code shown in this post.</description>
		<content:encoded><![CDATA[<p>Chuck&mdash;My overlay code here produces a &#8220;truecolor&#8221; image, which is an M-by-N-by-3 array.  The first plane is the red component, the second plane is the green component, and the third plane is the blue component.  The color of each image pixel is determined directly from these values, rather than indirectly via the figure colormap.  Unfortunately, this means that colorbar doesn&#8217;t work directly with such images.</p>
<p>So you need to do little extra work.  One approach is to display the image as you already do, using <tt>imagesc</tt> and the desired colormap.  Call <tt>imagesc</tt> with an output argument so you can save the handle to the created image object.  Then call colorbar.  Finally, set the CData of the image object to the overlay image created using the code shown in this post.</p>
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		<title>By: Chuck</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21955</link>
		<dc:creator>Chuck</dc:creator>
		<pubDate>Thu, 09 Jul 2009 03:17:13 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21955</guid>
		<description>Hello:

This overlay looks to be just about what I need.
I have a grayscale image that I currently use imagesc to display, using a stock colormap (jet). The values vary from 0 to perhaps 0.010 across the image. However, my object does not fill the entire image. All pixels outside the object are set to 0 using a mask. The data displayed is an error signal at each pixel.

Now, the issue is that as my object improves, the error at some (many, I hope) pixels approaches 0, and so those pixels are indistinguishable form the background or masked-off areas outside the object. I could set the masked areas to -1, and use CLIMS 0 to 0.010, but this still sets the masked areas to the 0 color.

Your overlay should do exactly what I need for the image. However, how do I now display a colorbar to indicate the original scaled colormap?

Thanks
Chuck</description>
		<content:encoded><![CDATA[<p>Hello:</p>
<p>This overlay looks to be just about what I need.<br />
I have a grayscale image that I currently use imagesc to display, using a stock colormap (jet). The values vary from 0 to perhaps 0.010 across the image. However, my object does not fill the entire image. All pixels outside the object are set to 0 using a mask. The data displayed is an error signal at each pixel.</p>
<p>Now, the issue is that as my object improves, the error at some (many, I hope) pixels approaches 0, and so those pixels are indistinguishable form the background or masked-off areas outside the object. I could set the masked areas to -1, and use CLIMS 0 to 0.010, but this still sets the masked areas to the 0 color.</p>
<p>Your overlay should do exactly what I need for the image. However, how do I now display a colorbar to indicate the original scaled colormap?</p>
<p>Thanks<br />
Chuck</p>
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		<title>By: Steve</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21892</link>
		<dc:creator>Steve</dc:creator>
		<pubDate>Thu, 18 Jun 2009 12:03:54 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21892</guid>
		<description>Rushil&#8212;In that case, you might want to explore &lt;a href="http://www.mathworks.com/access/helpdesk/help/techdoc/visualize/f3-6010.html" rel="nofollow"&gt;other options for transparent object display&lt;/a&gt; in MATLAB.</description>
		<content:encoded><![CDATA[<p>Rushil&mdash;In that case, you might want to explore <a href="http://www.mathworks.com/access/helpdesk/help/techdoc/visualize/f3-6010.html" rel="nofollow">other options for transparent object display</a> in MATLAB.</p>
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		<title>By: Rushil</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21889</link>
		<dc:creator>Rushil</dc:creator>
		<pubDate>Thu, 18 Jun 2009 09:11:24 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21889</guid>
		<description>Steve,

Yes, that is what I am looking to do but My "Mask" is not an image, it is a contour of densities (from the contourf function)so is there any way I can adapt what you had showed in "Image overlay using transparency" to suit my task?

Thank you for your help.

Rushil</description>
		<content:encoded><![CDATA[<p>Steve,</p>
<p>Yes, that is what I am looking to do but My &#8220;Mask&#8221; is not an image, it is a contour of densities (from the contourf function)so is there any way I can adapt what you had showed in &#8220;Image overlay using transparency&#8221; to suit my task?</p>
<p>Thank you for your help.</p>
<p>Rushil</p>
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	<item>
		<title>By: Steve</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21885</link>
		<dc:creator>Steve</dc:creator>
		<pubDate>Wed, 17 Jun 2009 13:17:18 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21885</guid>
		<description>Rushil&#8212;Your comment about "seeing the image partially" makes me think you might be interested in displaying one image transparently over another.  See &lt;a href="http://blogs.mathworks.com/steve/2009/02/18/image-overlay-using-transparency/" rel="nofollow"&gt;this post&lt;/a&gt; for examples.</description>
		<content:encoded><![CDATA[<p>Rushil&mdash;Your comment about &#8220;seeing the image partially&#8221; makes me think you might be interested in displaying one image transparently over another.  See <a href="http://blogs.mathworks.com/steve/2009/02/18/image-overlay-using-transparency/" rel="nofollow">this post</a> for examples.</p>
]]></content:encoded>
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	<item>
		<title>By: Rushil</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21884</link>
		<dc:creator>Rushil</dc:creator>
		<pubDate>Wed, 17 Jun 2009 13:12:22 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21884</guid>
		<description>Thanks for your reply Steve,

Here one can overlay a binary image as a mask. I have a similar task at hand, only difference being my "mask" needs to be multi-valued, not binary. It has certain gray levels too, currently it has about 3 levels between black(0) and white (1). The data I will be using to plot a mask is not discreet with zeros and ones. What i need is when the value is 0.5 i can see the image partially. I was thinking of doing this pixel wise, and rebuilding a new image while checking for values of the mask. What do you think?

Thank you.</description>
		<content:encoded><![CDATA[<p>Thanks for your reply Steve,</p>
<p>Here one can overlay a binary image as a mask. I have a similar task at hand, only difference being my &#8220;mask&#8221; needs to be multi-valued, not binary. It has certain gray levels too, currently it has about 3 levels between black(0) and white (1). The data I will be using to plot a mask is not discreet with zeros and ones. What i need is when the value is 0.5 i can see the image partially. I was thinking of doing this pixel wise, and rebuilding a new image while checking for values of the mask. What do you think?</p>
<p>Thank you.</p>
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	<item>
		<title>By: Steve</title>
		<link>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21883</link>
		<dc:creator>Steve</dc:creator>
		<pubDate>Wed, 17 Jun 2009 12:33:29 +0000</pubDate>
		<guid>http://blogs.mathworks.com/steve/2006/03/28/image-overlays/#comment-21883</guid>
		<description>Rushil&#8212;Sure, this technique could be extended to multiple levels.  Can you be more specific about the task and about what part you need help with?</description>
		<content:encoded><![CDATA[<p>Rushil&mdash;Sure, this technique could be extended to multiple levels.  Can you be more specific about the task and about what part you need help with?</p>
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