Differences in libraw behaviour between 0.19.5 and 0.20

Hi,
I recently upgraded from 0.19.5 to 0.20.0 and I noticed the difference in rendered sRGB output for many camera phone shot DNG files. I also noticed differences in the rgb_cam, cam_xyz and pre_mul values returned. I wanted to confirm if this is indeed intentional or a bug.

You can find a DNG file and the accompanying sRGB PNG files at this location below:
https://drive.google.com/drive/folders/1XiixDdUnsPY2TKcN-DzshNX2EmnA-EDY...

The output_params settings are below:

rp.imgdata.params.use_camera_wb = 1; // Use As Shot White Balance
rp.imgdata.params.output_bps = 16; // 16-bit output
rp.imgdata.params.no_auto_bright = 1; // Do not contrast stretch the image
rp.imgdata.params.output_color = 1; // sRGB space
rp.imgdata.params.gamm[0] = 1/2.4; // power for sRGB
rp.imgdata.params.gamm[1] = 12.92; // toe slope for sRGB

Also, for an Sony F828 camera with a BGRE pattern, the visible size reported in 0.20 was 3287x2460 but in 0.19.5 it was 3288x2460.

I can send additional files if needed.

Regards,
Dinesh

Forums: 

rgb_cam reported as identity matrix

I noticed there were a bunch of changes made to DNG processing. I am not sure if there are any changes I need to be making to the source code for this.

1) Many smartphone-produced

1) Many smartphone-produced DNG files has 'unusual' order of color data, the 1st one is daylight matrix, the 2nd one is for incandescent.
The old code (LibRaw 0.19/dcraw.c) always uses the last colordata (ColorMatrix) seen in the file. This works fine for Adobe-DNG-SDK-produced files (daylight colormatrix is the last one), but not with files where ColorMatrix1/ColorMatrix2 order is reversed.
Also, if several different sub-images are present in the DNG file with separate (own) colordata, the old code (again) uses the last one ColorMatrix specified

In the LibRaw 0.20 correct color matrix selection is implemented in both cases.

2) Visible size (or margins size) has changed in 0.20 for many cameras:
- for some cameras, vendor specified size is used instead of hardcoded one
- for all Bayer cameras margins are rounded to multiple of 2
- for all X-Trans cameras margins are rounded to multiple of 6

The last two changes is because of ambiguity in previous version: since LibRaw 0.20 bayer(/X-Trans) pattern is the same for both possible coordinate systems (entire area/visible area)

-- Alex Tutubalin

DNG Behaviour

Alex,
So is the old DNG processing behaviour a bug which has been fixed in the new code? Because the colours in the rendered sRGB image with 0.20 appear duller than 0.19.5.

But, I am surprised why the rgb_cam is being returned as an identity matrix. There was a bunch of changes made to DNG Frame Selection. I want to ensure that I do not have to add any additional code to ensure the correct frame and the properties corresponding to it are selected.

Is there a way to fallback on 0.19.5 behaviour? I see there is ifdef'ed code to fallback to use auto_ptr vs unique_ptr. Is there similar for old DNG processing?

Regards,
Dinesh

I do not see that processing

I do not see that processing result is dull

Here is the file processed with LibRaw 0.19.5 (dcraw_emu -w -T): https://www.dropbox.com/s/efh2f1rkukunuif/screenshot%202020-10-13%2016.2...

Here is LibRaw 0.20 processing (with daylight WB): https://www.dropbox.com/s/6x7l71j1e9f90s1/screenshot%202020-10-13%2016.2...

Please note that 'camera matrix' is used for DNG files if use_camera_matrix is either default (1) or greater.

-- Alex Tutubalin

Thanks!

Alex,
Thanks for sharing those. The colors in the 0.20 version do appear muted compared to 0.19 in my opinion. The output_params settings I am using the camera white balance and not d65. The use_camera_matrix setting is the same as before.

I am getting very similar results to libraw when I attempt to generate an sRGB image using my custom pipeline and the metadata that libraw has returned.

I wanted to confirm that the new behaviour is expected and getting rgb_cam as an identity matrix is valid because it does not seem intuitive to me.

Regards
Dinesh

It is not identity if params

It is not identity if params are set correctly, this code piece propagates cmatrix to rgb_cam:

  if ((use_camera_matrix & (((use_camera_wb || dng_version)?0:1) | 0x2)) &&
      cmatrix[0][0] > 0.125)
  {
    memcpy(rgb_cam, cmatrix, sizeof cmatrix);
...

-- Alex Tutubalin

This code is (indeed)

This code is (indeed) executed and rgb_cam becomes:

-		rgb_cam	0x00000128c200b044 {0x00000128c200b044 {1.60388803, -0.595357001, -0.00853104331, 0.00000000}, 0x00000128c200b054 {...}, ...}	float[3][4]
+		[0]	0x00000128c200b044 {1.60388803, -0.595357001, -0.00853104331, 0.00000000}	float[4]
+		[1]	0x00000128c200b054 {-0.145714581, 1.32941270, -0.183698103, 0.00000000}	float[4]
+		[2]	0x00000128c200b064 {0.0402970426, -0.722867191, 1.68257010, 0.00000000}	float[4]

-- Alex Tutubalin

Not really seeing this change at my end

Alex,
I am not really seeing this behaviour on Windows. I am attaching three screenshots from VS debugger.

color struct after unpack()

+		cam_mul	0x000000fbf3763464 {2.08979583, 1.00000000, 1.78397214, 0.00000000}	float[4]
+		pre_mul	0x000000fbf3763474 {2.35568857, 1.00068939, 1.55817533, 0.00000000}	float[4]
+		cmatrix	0x000000fbf3763484 {0x000000fbf3763484 {1.60388803, -0.595357001, -0.00853104331, 0.00000000}, 0x000000fbf3763494 {...}, ...}	float[3][4]
+		ccm	0x000000fbf37634b4 {0x000000fbf37634b4 {0.00000000, 0.00000000, 0.00000000, 0.00000000}, 0x000000fbf37634c4 {...}, ...}	float[3][4]
-		rgb_cam	0x000000fbf37634e4 {0x000000fbf37634e4 {1.00000000, 0.00000000, 0.00000000, 0.00000000}, 0x000000fbf37634f4 {...}, ...}	float[3][4]
+		[0]	0x000000fbf37634e4 {1.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
+		[1]	0x000000fbf37634f4 {0.00000000, 1.00000000, 0.00000000, 0.00000000}	float[4]
+		[2]	0x000000fbf3763504 {0.00000000, 0.00000000, 1.00000000, 0.00000000}	float[4]
-		cam_xyz	0x000000fbf3763514 {0x000000fbf3763514 {0.00000000, 0.00000000, 0.00000000}, 0x000000fbf3763520 {0.00000000, ...}, ...}	float[4][3]
+		[0]	0x000000fbf3763514 {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[1]	0x000000fbf3763520 {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[2]	0x000000fbf376352c {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[3]	0x000000fbf3763538 {0.00000000, 0.00000000, 0.00000000}	float[3]

params struct before dcraw_process

+		gamm	0x000000fbf373f288 {0.41666666666666669, 12.920000000000000, 0.0000000000000000, 0.0000000000000000, ...}	double[6]
+		user_mul	0x000000fbf373f2b8 {0.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
		shot_select	0	unsigned int
		bright	1.00000000	float
		threshold	0.00000000	float
		half_size	0	int
		four_color_rgb	0	int
		highlight	0	int
		use_auto_wb	0	int
		use_camera_wb	1	int
		use_camera_matrix	1	int
		output_color	1	int
+		output_profile	0x0000000000000000 <NULL>	char *
+		camera_profile	0x0000000000000000 <NULL>	char *

color struct after dcraw_process()

+		cam_mul	0x000000fbf3763464 {2.08979583, 1.00000000, 1.78397214, 0.00000000}	float[4]
+		pre_mul	0x000000fbf3763474 {2.08979583, 1.00000000, 1.78397214, 1.00000000}	float[4]
+		cmatrix	0x000000fbf3763484 {0x000000fbf3763484 {1.60388803, -0.595357001, -0.00853104331, 0.00000000}, 0x000000fbf3763494 {...}, ...}	float[3][4]
-		ccm	0x000000fbf37634b4 {0x000000fbf37634b4 {0.00000000, 0.00000000, 0.00000000, 0.00000000}, 0x000000fbf37634c4 {...}, ...}	float[3][4]
+		[0]	0x000000fbf37634b4 {0.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
+		[1]	0x000000fbf37634c4 {0.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
+		[2]	0x000000fbf37634d4 {0.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
-		rgb_cam	0x000000fbf37634e4 {0x000000fbf37634e4 {1.00000000, 0.00000000, 0.00000000, 0.00000000}, 0x000000fbf37634f4 {...}, ...}	float[3][4]
+		[0]	0x000000fbf37634e4 {1.00000000, 0.00000000, 0.00000000, 0.00000000}	float[4]
+		[1]	0x000000fbf37634f4 {0.00000000, 1.00000000, 0.00000000, 0.00000000}	float[4]
+		[2]	0x000000fbf3763504 {0.00000000, 0.00000000, 1.00000000, 0.00000000}	float[4]
-		cam_xyz	0x000000fbf3763514 {0x000000fbf3763514 {0.00000000, 0.00000000, 0.00000000}, 0x000000fbf3763520 {0.00000000, ...}, ...}	float[4][3]
+		[0]	0x000000fbf3763514 {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[1]	0x000000fbf3763520 {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[2]	0x000000fbf376352c {0.00000000, 0.00000000, 0.00000000}	float[3]
+		[3]	0x000000fbf3763538 {0.00000000, 0.00000000, 0.00000000}	float[3]

My workflow is:
open_file()
unpack()
// Set params
dcraw_process()
dcraw_make_mem_image()

Is this something to do with how the library is compiled?

Regards,
Dinesh

cmatrix is extracted

cmatrix is extracted

Could you please verify that the code snippet (memcpy from cmatrix to rgb_cam) is executed (or not)?

-- Alex Tutubalin

Thanks!

Alex,
Thanks for this. Once I applied this fix, the rgb_cam appears to be populated as you expected. The value is different than 0.19.5 but that appears to be expected based on the DNG fixes you made.

There does appear to be a bug with raw-identify though. When I dumped out information about this file, no information gets printed past "MakerNotes WB data". The executable appears to exit. Even the line "fprintf(outfile, "\nXYZ->CamRGB matrix:\n");" is not executed. The last few lines displayed are:

Filter pattern: RGGBRGGBRGGBRGGB
Highlight linearity limits: 3827 3827 3827 3827
Makernotes WB data: coeffs EVs
As shot 495 256 324 256 0.95 0.00 0.34 0.00

Happens even with NEF files. Appears to be an issue with printing out WB_Coeffs. I am on Windows.

Update

Removing the WB_Coeff printing results in the rest of the raw-identify code working.

Dinesh