<div>I want to create an  4 byte image with different alpha values and   use it as  texture .</div><div><br></div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre">        </span>vtkImageData*  pImage=vtkImageData::New();</div>
<div><span class="Apple-tab-span" style="white-space:pre">        </span>pImage-&gt;SetDimensions(100,100,1);<br></div><div><span class="Apple-tab-span" style="white-space:pre">        </span>pImage-&gt;SetScalarTypeToUnsignedChar();<br>
</div><div><span class="Apple-tab-span" style="white-space:pre">        </span>pImage-&gt;SetNumberOfScalarComponents(4);</div><div><span class="Apple-tab-span" style="white-space:pre">        </span>pImage-&gt;AllocateScalars();</div>
<div><span class="Apple-tab-span" style="white-space:pre">        </span>vtkUnsignedCharArray  *ptr=(vtkUnsignedCharArray *)pImage-&gt;GetPointData()-&gt;GetScalars();<br></div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre">        </span>int count=ptr-&gt;GetSize()/4;<br>
</div><div><span class="Apple-tab-span" style="white-space:pre">        </span>int i=0;</div><div><span class="Apple-tab-span" style="white-space:pre">        </span>while (i&lt;count)</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>{</div>
<div><span class="Apple-tab-span" style="white-space:pre">                        </span>unsigned char  data[4];</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span>data[0]=0;</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span>data[1]=255;</div>
<div><span class="Apple-tab-span" style="white-space:pre">                        </span>data[2]=0;</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span>data[3]=i%125;</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span><br>
</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span>ptr-&gt;SetTupleValue(i,(const unsigned char*)data);</div><div><span class="Apple-tab-span" style="white-space:pre">                        </span>i++;</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>}<br>
</div><div><div><span class="Apple-tab-span" style="white-space:pre">                </span>vtkImageMapToColors* pImageColor=vtkImageMapToColors::New();</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>pImageColor-&gt;SetInput(pImage);</div>
<div><span class="Apple-tab-span" style="white-space:pre">                </span>pImageColor-&gt;SetOutputFormatToRGBA();</div><div><br></div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre">                </span>vtkLookupTable* table=vtkLookupTable::New();</div>
<div><span class="Apple-tab-span" style="white-space:pre">                </span>float maxColor=255;</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetRange(0,maxColor);</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetTableValue(0,1,0,0,1);</div>
<div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetTableValue(1,0,0,1,0);</div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetValueRange(1,0);</div>
<div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetSaturationRange(1,0);</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetHueRange(1.0,0);</div><div><span class="Apple-tab-span" style="white-space:pre">                </span>table-&gt;SetAlphaRange(1,0);</div>
<div><br></div><div><br></div><div>But the result is confusing. a red texture  is created.whats the table range for?  one component or 4 component?</div><div>thanks.</div></div>