+/**
+ * \ingroup gdcmHeader
+ * \brief builts Red/Green/Blue/Alpha LUT from Header
+ * \ when (0028,0004),Photometric Interpretation = [PALETTE COLOR ]
+ * \ and (0028,1101),(0028,1102),(0028,1102)
+ * \ - xxx Palette Color Lookup Table Descriptor - are found
+ * \ and (0028,1201),(0028,1202),(0028,1202)
+ * \ - xxx Palette Color Lookup Table Data - are found
+ * \warning does NOT deal with :
+ * \ 0028 1100 Gray Lookup Table Descriptor (Retired)
+ * \ 0028 1221 Segmented Red Palette Color Lookup Table Data
+ * \ 0028 1222 Segmented Green Palette Color Lookup Table Data
+ * \ 0028 1223 Segmented Blue Palette Color Lookup Table Data
+ * \ no known Dicom reader deals with them :-(
+ * @return a RGBA Lookup Table
+ */
+unsigned char * gdcmHeader::GetLUTRGBA(void) {
+// Not so easy : see
+// http://www.barre.nom.fr/medical/dicom2/limitations.html#Color%20Lookup%20Tables
+
+// if Photometric Interpretation # PALETTE COLOR, no LUT to be done
+ if (GetEntryByNumber(0x0028,0x0004) != "PALETTE COLOR ") {
+ return NULL;
+ }
+ int lengthR, debR, nbitsR;
+ int lengthG, debG, nbitsG;
+ int lengthB, debB, nbitsB;
+
+// Get info from Lut Descriptors
+// (the 3 LUT descriptors may be different)
+ std::string LutDescriptionR = GetEntryByNumber(0x0028,0x1101);
+ if (LutDescriptionR == GDCM_UNFOUND)
+ return NULL;
+ std::string LutDescriptionG = GetEntryByNumber(0x0028,0x1102);
+ if (LutDescriptionG == GDCM_UNFOUND)
+ return NULL;
+ std::string LutDescriptionB = GetEntryByNumber(0x0028,0x1103);
+ if (LutDescriptionB == GDCM_UNFOUND)
+ return NULL;
+
+ std::vector<std::string> tokens;
+
+ tokens.erase(tokens.begin(),tokens.end()); // clean any previous value
+ Tokenize (LutDescriptionR, tokens, "\\");
+ lengthR=atoi(tokens[0].c_str()); // Red LUT length in Bytes
+ debR =atoi(tokens[1].c_str()); // subscript of the first Lut Value
+ nbitsR =atoi(tokens[2].c_str()); // Lut item size (in Bits)
+ tokens.clear();
+
+ tokens.erase(tokens.begin(),tokens.end()); // clean any previous value
+ Tokenize (LutDescriptionG, tokens, "\\");
+ lengthG=atoi(tokens[0].c_str()); // Green LUT length in Bytes
+ debG =atoi(tokens[1].c_str());
+ nbitsG =atoi(tokens[2].c_str());
+ tokens.clear();
+
+ tokens.erase(tokens.begin(),tokens.end()); // clean any previous value
+ Tokenize (LutDescriptionB, tokens, "\\");
+ lengthB=atoi(tokens[0].c_str()); // Blue LUT length in Bytes
+ debB =atoi(tokens[1].c_str());
+ nbitsB =atoi(tokens[2].c_str());
+ tokens.clear();
+
+ // Load LUTs into memory, (as they were stored on disk)
+ unsigned char *lutR = (unsigned char *)
+ GetEntryVoidAreaByNumber(0x0028,0x1201);
+ unsigned char *lutG = (unsigned char *)
+ GetEntryVoidAreaByNumber(0x0028,0x1202);
+ unsigned char *lutB = (unsigned char *)
+ GetEntryVoidAreaByNumber(0x0028,0x1203);
+
+ if (!lutR || !lutG || !lutB ) {
+ return NULL;
+ }
+ // forge the 4 * 8 Bits Red/Green/Blue/Alpha LUT
+
+ unsigned char *LUTRGBA = (unsigned char *)calloc(1024,1); // 256 * 4 (R, G, B, Alpha)
+ if (!LUTRGBA) {
+ return NULL;
+ }
+ memset(LUTRGBA, 0, 1024);
+ // Bits Allocated
+ int nb;
+ std::string str_nb = GetEntryByNumber(0x0028,0x0100);
+ if (str_nb == GDCM_UNFOUND ) {
+ nb = 16;
+ } else {
+ nb = atoi(str_nb.c_str() );
+ }
+ int mult;
+
+ if (nbitsR==16 && nb==8) // when LUT item size is different than pixel size
+ mult=2; // high byte must be = low byte
+ else // See PS 3.3-2003 C.11.1.1.2 p 619
+ mult=1;
+
+ // if we get a black image, let's just remove the '+1'
+ // from 'i*mult+1' and check again
+ // if it works, we shall have to check the 3 Palettes
+ // to see which byte is ==0 (first one, or second one)
+ // and fix the code
+ // We give up the checking to avoid some overhead
+ unsigned char *a;
+ int i;
+
+ a = LUTRGBA+0;
+ for(i=0;i<lengthR;i++) {
+ *a = lutR[i*mult+1];
+ a+=4;
+ }
+ a = LUTRGBA+1;
+ for(i=0;i<lengthG;i++) {
+ *a = lutG[i*mult+1];
+ a+=4;
+ }
+ a = LUTRGBA+2;
+ for(i=0;i<lengthB;i++) {
+ *a = lutB[i*mult+1];
+ a+=4;
+ }
+ a = LUTRGBA+3;
+ for(i=0;i<256;i++) {
+ *a = 1; // Alpha component
+ a+=4;
+ }
+
+ //How to free the now useless LUTs?
+
+ //free(LutR); free(LutB); free(LutG); // Seg Fault when used
+ return(LUTRGBA);
+}
+