Obtain an Entity’s RGB Color using ObjectARX

by Fenton Webb

Issue

Is there a way to get an entity’s RGB color? The color() function returns an AcCmColor object. How do you get the RGB values from this?

Solution

There are several ways colors can be applied to entities. If the entity is using the color index (ACI) then you can use acedGetRgb() to get RGB vaules. Below is an example that gets the color method and displays the RGB values for entities using ACI or True Color. If the entity was using byLayer then you would have to access the layer to get the color information.

static void ASDKwb_test(void)    {      ads_name eName;      ads_point pnt1;      // select the entity to extract the color      int res = acedEntSel(_T("nselect an entity"), eName, pnt1);       // if ok      if (res == RTNORM)      {        AcDbObjectId oId;        // convert the ename to an object id        acdbGetObjectId(oId, eName);        // open for read        AcDbObjectPointer pEnt(oId, AcDb::kForRead);        // if ok        if (pEnt.openStatus() == Acad::eOk)        {          // get the color          AcCmColor color = pEnt->color();               Adesk::UInt8 blue, green, red;          Adesk::UInt16 ACIindex;          long acirgb, r,g,b;                // get the RGB value as an Adesk::Int32          Adesk::Int32 nValue = color.color();               // now extract the values          AcCmEntityColor::ColorMethod cMethod;          cMethod = color.colorMethod();          switch(cMethod)          {          case AcCmEntityColor::kByColor :            // now convert back to the original values, first 8 bits blue            acutPrintf(_T("nEntity using True Color"));            blue = nValue;            acutPrintf(_T("nblue value = %i"), blue);             // now move nValue right 8 bits, green            nValue = nValue>>8;            // now get the green            green = nValue;            acutPrintf(_T("ngreen value = %i"), green);            // move right to the next 8 bits red            nValue = nValue>>8;            red = nValue;            acutPrintf(_T("nred value = %i"), red);             break;                    case AcCmEntityColor::kByACI :            ACIindex = color.colorIndex();             acutPrintf(_T("nEntity using ACI, number: %i", ACIindex));            acirgb = acedGetRGB ( ACIindex );            r = ( acirgb & 0xffL );             acutPrintf(_T("nred value = %i"), r);            g = ( acirgb & 0xff00L ) >> 8;            acutPrintf(L"ngreen value = %i"), g);            b = acirgb >> 16;            acutPrintf(L"nblue value = %i"), b);            break;                    case AcCmEntityColor::kByLayer :            acutPrintf(_T("nEntity Color is by layer"));            break;                    default :            acutPrintf(_T("nEntity not using ACI, byLayer or ByColor"));             break;          }        }      }     }