Import Cbf Byte_offset compressed images

//*************************************************************************************************
//	This function imports Cbf file with byte_offset compression
// see: http://www.bernstein-plus-sons.com/software/CBF/doc/CBFlib.html#3.3.3
// for compression description and lots of other information. 
// tested on Pilatus 2M images (from PSI)
//*************************************************************************************************
Function LoadCbfCompresedImage(PathName,FileNameToLoad, WaveNameToCreate)
	string PathName,  FileNameToLoad, WaveNameToCreate
	//this function loads and uncompresses the Cbf byte_offset compressed file format with:
	// conversions="x-CBF_BYTE_OFFSET";Content-Transfer-Encoding=BINARY;
        //X-Binary-Element-Type="signed 32-bit integer";X-Binary-Element-Byte-Order=LITTLE_ENDIAN;
	//Searches for start of binary data, checks how much data there should be and creates 1D wave output wave (stream) 
        //     with uncompressed data in the current data folder. 
	variable SkipBytes
	variable filevar
	variable bufSize 
	variable sizeToExpect
	string testLine
	//locate start of the binary data
	open /R/P=$(PathName) filevar as FileNameToLoad
	testLine=""
	testLine=PadString (testLine, 16800, 0x20)
	FBinRead filevar, testLine
	close filevar
	SkipBytes=strsearch(testLine, "\014\032\004\325" , 0)+4		//this is string I found in test images
	if(SkipBytes<5)										//string not found...
		SkipBytes=strsearch(testLine, "\012\026\004\213" , 0)+4	//this is per http://www.bernstein-plus-sons.com/software/CBF/doc/CBFlib.html#3.2.2 what should be there. Go figure... 
	endif
	if(SkipBytes<5)
		Abort "Failed to find start of binary section in the Cbf file"	//string still not found. This is problem. 
	endif
	//Figure out now how much data are we expecting
	//    this header is quite messy, let's clean ti up a bit
	testLine=ReplaceString("\r\n\r\n", testLine, ";")
	testLine=ReplaceString("\r\n", testLine, ";")
	testLine=ReplaceString("#", testLine, "")
	testLine=ReplaceString(";;;;", testLine, ";")
	testLine=ReplaceString(";;;", testLine, ";")
	testLine=ReplaceString(";;", testLine, ";")
	testLine = ReplaceString(":", testLine, "=")
	sizeToExpect = NumberByKey("X-Binary-Number-of-Elements", testLine, "=", ";")
	//read the data in binary free wave so we can use them here
	Open /Z/R/P=$(PathName)/T="????" filevar as FileNameToLoad
	if (V_flag)
		close filevar
		Abort "Cannot open file, something is wrong here"		// could not open file
	endif
	FSetPos fileVar, SkipBytes								//start of the image
	FStatus fileVar
	bufSize = V_logEOF-V_filePos							//this is how mcuh data we have in the image starting at the binary data start
	make/B/O/N=(bufSize)/Free BufWv						//signed 1 byte wave for the data
	make/O/N=(sizeToExpect)/Free ResultImage				//here go teh converted singed integers. Note, they can be 8, 16, or 32 bits. 64bits not supported here. 
	FBinRead/B=1/F=1 fileVar, BufWv						//read 1 Byte each into singed integers wave
	close filevar
	//and not decompress the data here 	
	variable i, j, PixelValue, ReadValue
	j=0												// j is index of the signed 1 byte wave (stream of data in) 
	PixelValue = 0										//value in current pixel in image. 
	For(i=0;i<(sizeToExpect);i+=1)							//i is index for output wave
		if(j>bufSize-1)
			break									//just in case, we run our of j. Should never happen
		endif
		ReadValue = BufWv[j]							//read 1 Byte integer
		if(ReadValue>-128)								//this is useable value if +/- 127
			PixelValue += ReadValue						//add to prior pixel value
			ResultImage[i] = PixelValue					//store in output stream
			j+=1										// move to another j point 
		elseif(ReadValue==-128)							// This is indicator that the difference did not fit in 1Byte, read 2 bytes and use those.
			j+=1										// move to another point to start reading the 2 bytes
			ReadValue = Conv2Bytes(BufWv[j],BufWv[j+1])	        //read and convert 2 Bytes in integer
			if(ReadValue>-32768)						// This is useable value, use these two bytes
				PixelValue += ReadValue					//add to prior pixel value
				ResultImage[i] = PixelValue				//store in output stream
				j+=2									//move to another j point  
			elseif(ReadValue==-32768)					// This is indicator that the difference did not fit in 2Bytes, read 4 bytes and use those.
				j+=2									//move to another point to start reading the 4 bytes 
				ReadValue = Conv4Bytes(BufWv[j],BufWv[j+1], BufWv[j+2], BufWv[j+3])		//read and convert next 4 Bytes in integer
				if(abs(ReadValue)<2147483648)				//this is correct value for 32 bits
					PixelValue += ReadValue				//add to prior pixel value
					ResultImage[i] = PixelValue			//store in output stream
					j+=4								//move to another j point 
				else									//abort, do not support 64 byte integers (no such detector exists... 
					abort "64 bits data are not supported"
				endif
			else
				print "error"
			endif
		else
			print "error"
		endif
	endfor
	Duplicate/O ResultImage, $(WaveNameToCreate)			
	//create wave user requested. Note, this is 1D wave and needs to be redimensioned to 2D wave (image). Could be done here... 
end
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static Function Conv2Bytes(B1,B2)		
	variable B1, B2
	//takes two signed integer bytes, and converts them to 16 bit signed integer, little-endian, two's complement signed interpretation
	//assume B1 is first byte for little-endian should be unsigned integer as it is the smaller part of the data
	//assume B2 contains the larger values and sign
	variable unsB1=(B1>=0) ? B1 : (256 + B1)	//this should convert two's complement signed interpretation to Usigned interpretation
	return unsB1 + 256*B2
end
//*************************************************************************************************
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static Function Conv4Bytes(B1,B2, B3, B4)		
	variable B1, B2, B3, B4
	//takes four signed integer bytes, and converts them to 32 bit signed integer, little-endian, two's complement signed interpretation
	//assume B1, B2, B3 are first bytes for little-endian should be unsigned integer as it is the smaller part of the data
	//assume B4 contains the larger values and sign
	variable unsB1=(B1>=0) ? B1 : (256 + B1)	//this should convert two's complement signed interpretation to Usigned interpretation
	variable unsB2=(B2>=0) ? B2 : (256 + B2)	//this should convert two's complement signed interpretation to Usigned interpretation
	variable unsB3=(B3>=0) ? B3 : (256 + B3)	//this should convert two's complement signed interpretation to Usigned interpretation
	return unsB1 + 256*unsB2 + 256*256*unsB3 + 256*256*256*B4
end
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