reading .raw with LibRaw iProcessor example

Submitted by santana on

Hello everyone,
I am trying to read a raw image with libraw using the example in the API page " https://www.libraw.org/docs/API-overview.html"
I wrote the following code and get a -2 file reading error.
I was able to read the same raw image with Python (fromfile) specifying bit ordering to 'big'. What should I do to read to do this with libraw in C++?

#include <iostream>
#include "libraw/libraw.h"
#include "libraw/libraw.h"
int main(int argc, char **argv)
{
	LibRaw iProcessor;
 
	// Open the file and read the metadata
	char *fname = (char *)"/home/santana/myraw.raw";
 
	int isOK = iProcessor.open_file(fname);
	std::cout << " is ok ? " << isOK << std::endl;
	printf("Image size: %d x %d\n", iProcessor.imgdata.sizes.width,  iProcessor.imgdata.sizes.height);
	iProcessor.unpack();
	// Convert from imgdata.rawdata to imgdata.image:
	iProcessor.raw2image();
	for (int i = 0; i < iProcessor.imgdata.sizes.iwidth * iProcessor.imgdata.sizes.iheight; i++)
	{
		printf("i=%d R=%d G=%d B=%d G2=%d\n", i, iProcessor.imgdata.image[i][0],
			   iProcessor.imgdata.image[i][1], iProcessor.imgdata.image[i][2],
			   iProcessor.imgdata.image[i][3]);
	}
 
	// Finally, let us free the image processor for work with the next image
	iProcessor.recycle();
 
	return EXIT_SUCCESS;
}

output :

is ok ? -2
Image size: 0 x 0

Forums: 

-2 is: LIBRAW_FILE

Submitted by lexa on

-2 is: LIBRAW_FILE_UNSUPPORTED

If your 'raw' file is just a sensor dump without metadata consider using open_bayer() call

-- Alex Tutubalin @LibRaw LLC

open_bayer : bufferdouble of real values

Submitted by santana on

Thank you Alex for your answer. I tried with open_bayer as I think the raw file has no metadata. With the code bellow I could see that readb as 1280000 values instead of 640000 for an image 800x8000. The final result with dcraw_process is not satisfactory. I wonder If and how I could retrieve the unpacked values and do the conversion myself. 

FILE *in = fopen(fname, "rb");
	fseek(in, 0, SEEK_END);
	unsigned fsz = ftell(in);
	unsigned char *buffer = (unsigned char *)malloc(fsz);
	if (!buffer)
		return 2;
	fseek(in, 0, SEEK_SET);
	unsigned readb = fread(buffer, 1, fsz, in);
	if (readb != fsz)
		return 3;
	std::cout << "readb" << readb << std::endl;
	LibRaw rp;
	rp.imgdata.params.output_tiff = 1;
	int ret = rp.open_bayer(buffer, fsz, 800, 800, 0, 0, 0, 0, 0,
							LIBRAW_OPENBAYER_BGGR, 0, 0, 0);
	if (ret != LIBRAW_SUCCESS)
		return 4;
	if ((ret = rp.unpack()) != LIBRAW_SUCCESS)
		printf("Unpack error: %d\n", ret);
 
	if ((ret = rp.dcraw_process()) != LIBRAW_SUCCESS)
		printf("Processing error: %d\n", ret);
 
	char outfn[256];
	sprintf(outfn, "%s.tif", fname);
	if (LIBRAW_SUCCESS != (ret = rp.dcraw_ppm_tiff_writer(outfn)))
		printf("Cannot write %s: %s\n", outfn, libraw_strerror(ret));
	else
		printf("Created %s\n", outfn);
 
	ret = rp.dcraw_process();
	// Check for error using LIBRAW_SUCCESS. I never get an error here
 
	ret = rp.dcraw_ppm_tiff_writer(fname);

santana

If your input data is 16 bit

Submitted by lexa on

If your input data is 16 bit (2 bytes per pixel), 1,280,000 bytes is expected....

-- Alex Tutubalin @LibRaw LLC

Also, if your file is 2 bytes

Submitted by lexa on

Also, if your file is 2 bytes per pixel, uncompressed, you do not need LibRaw to read source data values. Your values are already here (in unsigned short format, probably you may need big/little-endian swap; I know nothing about your images and your camera)

-- Alex Tutubalin @LibRaw LLC

swapt little endian to big endian

Submitted by santana on

Thank you again for your answers.
Actually, yes the data is encoded in int16.
I was able to read it in python swap bit ordering to bi endian. Any idea how I can achieve this in c++ ?
Also my guess for taking 2 bites with go for two consecutive bytes. Does this seam reasonable. I don' have all format specifications in hand.

santana

For byte swapping use

Submitted by kmilos (not verified) on

For byte swapping use something like ntohs() (actually this converts from big endian to your machine/host endianness, so it might be a noop if your machine is big endian as well) or, depending on your system/compiler, some incarnation of the bswap16() intrinsic/bultin function (e.g. __builtin_bswap16() for GCC, _byteswap_ushort() for MSVC, etc.)

__builtin_bswap16() did great

Submitted by santana on

Thank you all for the answers. I read the binary with native C++ fstream (800x800 = 640000 values). then used __builtin_bswap16() to swap and obtain my bayer data which I was able to convert to RGB,
Many thanks

santana