<div dir="ltr">Looks like I was wrong about the second table. It should use this:<div><br></div><div><div> table2 ->SetValueRange(0.0,1.0);</div><div> table2 ->SetAlphaRange(0.5,0.5);</div></div><div><br></div><div>Ideally, it would be nice if VTK provided a way to simply add the</div><div>two colors together, but the best you can do is use the alpha to</div><div>make VTK multiply the images by 0.5 before adding them. As a</div><div>result, you end up with grey instead of white.</div><div><br></div><div> - David</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Apr 20, 2016 at 1:15 AM, David Gobbi <span dir="ltr"><<a href="mailto:david.gobbi@gmail.com" target="_blank">david.gobbi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Jothy,<div><br></div><div>I see this mistake a lot... people try to blend images by setting the alpha of both images to 0.5. That's wrong. If you want to blend images, then the first image should be opaque, and the second image should have an alpha of 0.5.<br><div><br></div><div>C = C1*(1 - alpha2) + C2*alpha2</div><div><br></div><div>The second mistake is that, if you want to blend complimentary colors, then you don't want the Value of the second image to be the ramp. Instead, you want the Alpha of the second image to be the ramp.</div><div><br></div><div><span class=""><div> // Create a GREEN lookup table</div><div> vtkSmartPointer<vtkLookupTable> table =</div><div> vtkSmartPointer<vtkLookupTable>::New();</div><div> table->SetHueRange(0.33333,0.33333);</div><div> table->SetSaturationRange(1.0,1.0);</div><div> table->SetValueRange(0.0,1.0);</div></span><div> table->SetAlphaRange(1.0,1.0); // make the bottom image opaque</div><span class=""><div> table->SetRampToLinear();</div><div> table->Build();</div><div><br></div><div> // Create a MAGENTA lookup table</div><div> vtkSmartPointer<vtkLookupTable>table2 =</div><div> vtkSmartPointer<vtkLookupTable>::New();</div><div> table2 ->SetHueRange(0.8333,0.8333);</div><div> table2 ->SetSaturationRange(1.0,1.0);</div></span><div> table2 ->SetValueRange(1.0,1.0); // use pure magenta, don't mix with black</div><div> table2 ->SetAlphaRange(0.0,1.0); // use an alpha ramp to blend the images</div><span class=""><div> table2 ->SetRampToLinear();</div><div> table2 ->Build();</div></span></div><span class="HOEnZb"><font color="#888888"><div><br></div></font></span><div><span class="HOEnZb"><font color="#888888">- David</font></span><div><div class="h5"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Apr 19, 2016 at 11:43 PM, Jothybasu Selvaraj <span dir="ltr"><<a href="mailto:jothybasu@gmail.com" target="_blank">jothybasu@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div style="font-family:verdana,sans-serif">Hi All</div><div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif">I am trying to overlay 2 registered images using complementary LUTs (magenta & green), so that the images will appear white where they match perfectly. However, I couldn't get the desired results. The image appears magenta where they match.</div><div style="font-family:verdana,sans-serif"><br>Can anyone find any mistakes in this?</div><div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif">Below are the LUTs I use:</div><div style="font-family:verdana,sans-serif"><br></div><div style="font-family:verdana,sans-serif"><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(0,128,0)">//</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">Create</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">a</span><span style="color:rgb(192,192,192)"> </span><font color="#008000">GREEN</font><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">lookup</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">table</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><span style="color:rgb(0,0,0)"><</span><span style="color:rgb(128,0,128)">vtkLookupTable</span><span style="color:rgb(0,0,0)">></span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">=</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><span style="color:rgb(0,0,0)"><</span><span style="color:rgb(128,0,128)">vtkLookupTable</span><span style="color:rgb(0,0,0)">>::</span><span style="color:rgb(0,0,0)">New</span><span style="color:rgb(0,0,0)">();</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="font-style:italic;color:rgb(0,0,0)">SetHueRange</span><span style="color:rgb(0,0,0)">(</span><span style="color:rgb(0,0,128)">0.33333</span><span style="color:rgb(0,0,0)">,</span><span style="color:rgb(0,0,128)">0.33333</span><span style="color:rgb(0,0,0)">);</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="font-style:italic;color:rgb(0,0,0)">SetSaturationRange</span><span style="color:rgb(0,0,0)">(</span><span style="color:rgb(0,0,128)">1.0</span><span style="color:rgb(0,0,0)">,</span><span style="color:rgb(0,0,128)">1.0</span><span style="color:rgb(0,0,0)">);</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="font-style:italic;color:rgb(0,0,0)">SetValueRange</span><span style="color:rgb(0,0,0)">(</span><span style="color:rgb(0,0,128)">0.0</span><span style="color:rgb(0,0,0)">,</span><span style="color:rgb(0,0,128)">1.0</span><span style="color:rgb(0,0,0)">);</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="font-style:italic;color:rgb(0,0,0)">SetAlpha</span><span style="color:rgb(0,0,0)">(</span><span style="color:rgb(0,0,128)">0.5</span><span style="color:rgb(0,0,0)">);</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="color:rgb(0,0,0)">SetRampToLinear</span><span style="color:rgb(0,0,0)">();</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">table</span><span style="color:rgb(0,0,0)">-></span><span style="font-style:italic;color:rgb(0,0,0)">Build</span><span style="color:rgb(0,0,0)">();</span></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(0,0,0)"><br></span></pre><pre style="margin-top:0px;margin-bottom:0px"><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(0,128,0)">//</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">Create</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">a</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">MAGENTA</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">lookup</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">table</span></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><span style="color:rgb(0,0,0)"><</span><span style="color:rgb(128,0,128)">vtkLookupTable</span><span style="color:rgb(0,0,0)">></span><span style="color:rgb(0,0,0)">table2</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,0)">=</span></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><span style="color:rgb(0,0,0)"><</span><span style="color:rgb(128,0,128)">vtkLookupTable</span><span style="color:rgb(0,0,0)">>::</span><span style="color:rgb(0,0,0)">New</span><span style="color:rgb(0,0,0)">();</span></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;font-style:italic;color:rgb(0,0,0)">SetHueRange</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">(</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">0.8333</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">,</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">0.8333</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">);</span><br></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;font-style:italic;color:rgb(0,0,0)">SetSaturationRange</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">(</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">1.0</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">,</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">1.0</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">);</span><br></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;font-style:italic;color:rgb(0,0,0)">SetValueRange</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">(</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">0.0</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">,</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">1.0</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">);</span><br></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;font-style:italic;color:rgb(0,0,0)">SetAlpha</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">(</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,128)">0.5</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">);</span><br></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">SetRampToLinear</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">();</span><br></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">table2</span><span style="font-family:verdana,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">-></span><span style="font-family:verdana,sans-serif;font-style:italic;color:rgb(0,0,0)">Build</span><span style="font-family:verdana,sans-serif;color:rgb(0,0,0)">();</span><br></pre>
<pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px">Any help is highly appreciated!</pre><pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px">Cheers</pre><pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px">Jothy</pre></pre>
<pre style="margin-top:0px;margin-bottom:0px"><br></pre></div></div></blockquote></div></div></div></div></div></div></div>
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