<div class="gmail_quote">On Thu, Feb 10, 2011 at 1:38 PM, Sara Rolfe <span dir="ltr"><<a href="mailto:smrolfe@u.washington.edu">smrolfe@u.washington.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word">Hello,<div><br></div><div>I'm attempting to overlay an image with color. I've had trouble finding documentation on this, either in ITK or VTK. The way I'm going about it is to scale the values of the image down and then use the add image filter to add the labels on top. I could then use VTK to create a corresponding colormap.</div>
<div><br></div><div>However, I'm getting stuck on something that should be very simple. My operations to combine the two images are failing. I think the problem is the <span style="font-family:Monaco;font-size:10px">SubtractConstantFromImageFilter. </span>I've checked the output and it looks like the constant is not being subtracted. The input to this filter is an image with a value of 0 for the background and 255 for the object. I'd like to change these to 0 and 1. The pixel type is unsigned char. I use the following:</div>
<div><span style="font-family:Monaco;font-size:10px"><br></span></div><div><span style="font-family:Monaco;font-size:10px"><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><span style="white-space:pre-wrap"> </span>SubFilterType::Pointer subFilter = SubFilterType::New();</div>
<div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><span style="white-space:pre-wrap"> </span>InputPixelType subValue = <span style="color:#1c00cf">254</span>;</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
<span style="white-space:pre-wrap"> </span>subFilter->SetConstant(subValue);</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><span style="white-space:pre-wrap"> </span>subFilter->SetInput( imageInverter->GetOutput() );</div>
<div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><span style="white-space:pre-wrap"> </span>subFilter->Update();</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
<br></div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><font face="Helvetica"><span style="font-size:medium">But the output image is still 0 - 255. Am I missing something simple? </span></font></div>
<div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><font face="Helvetica"><span style="font-size:medium"><br></span></font></div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
<font face="Helvetica"><span style="font-size:medium">Also, is there a better way to accomplish this task, or any examples showing something similar?</span></font></div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
<font face="Helvetica"><span style="font-size:medium"><br></span></font></div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><font face="Helvetica"><span style="font-size:medium">Thanks,</span></font></div>
<div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px"><font face="Helvetica"><span style="font-size:medium">Sara</span></font></div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
<font face="Helvetica"><span style="font-size:medium"><br></span></font></div></span></div></div></blockquote><meta http-equiv="content-type" content="text/html; charset=utf-8">Can you provide a compilable code snippet? I'm also not sure what you mean by "overlay with color"?</div>
<div class="gmail_quote"><br></div><div class="gmail_quote">Something that jumps out is that if you subtract 254 from an unsigned char you will be assigning a negative value to an unsigned char which is undefined.</div><div class="gmail_quote">
<br></div><div class="gmail_quote">If all you are trying to do is map (0-255) to (0-1) you could use itkRescaleIntensityImageFilter</div><div class="gmail_quote"><meta http-equiv="content-type" content="text/html; charset=utf-8"><a href="http://www.itk.org/Wiki/ITK/Examples/ImageProcessing/RescaleIntensityImageFilter">http://www.itk.org/Wiki/ITK/Examples/ImageProcessing/RescaleIntensityImageFilter</a></div>
<div class="gmail_quote"><a href="http://www.itk.org/Wiki/ITK/Examples/ImageProcessing/RescaleIntensityImageFilter"></a><br clear="all">David </div>