Montage not maintaining 16 bit depth

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digitalis99
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Montage not maintaining 16 bit depth

Post by digitalis99 »

I'm a 3D animator that creates large still image renders using a tile rendering process. The tiles created by my application are 16bits per channel EXR's. I'm trying to use montage to stitch the tiles together into the final image. For some reason, the bit depth seems to be down-converting to 8bits per channel, no matter what options I feed to montage. I'm using montage from ImageMagick-6.9.2-Q16-HDRI. An example of the command I feed to montage is:
montage.exe cropped_spherical-lighting-test1.*000001.exr -geometry "100x200+0+0<" -tile 20x5 output.exr
I've put together a .zip of the correct output, a set of tiles, and an incorrect output as generated by montage. You may download it here:
http://www.mastermindpro.com/montage_problem.zip

If you open both of the output EXR's in Photoshop and drop the exposure to -5, you'll see the correct output has dynamic range whereas the output from montage...doesn't. :?

I should note that I have to do an additional step (convert.exe) to crop the output tiles prior to using montage to stitch them together. I think convert is maintaining the bit depth detail correctly (which you can see from examining the cropped tiles), so I'm focusing my troubleshooting on montage. Let me know if that is mistaken.
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fmw42
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

It might be a restriction of exr output and/or using Windows or your version of OpenEXR? Does the following work for you?

The following works fine for me under IM 6.9.2.6 Q16 Mac OSX. I get a 16-bit output.

Code: Select all

montage cropped_spherical-lighting-test1.+AA+000001.exr cropped_spherical-lighting-test1.+AA+000001.exr cropped_spherical-lighting-test1.+AA+000001.exr -geometry "100x200+0+0<" -tile 3x1 tmp.png
identify -verbose tmp.png
Image: tmp.png
  Format: PNG (Portable Network Graphics)
  Mime type: image/png
  Class: DirectClass
  Geometry: 300x200+0+0
  Units: Undefined
  Type: TrueColor
  Endianess: Undefined
  Colorspace: sRGB
  Depth: 16-bit
  Channel depth:
    red: 15-bit
    green: 15-bit
    blue: 16-bit
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digitalis99
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

I should clarify, the output image from montage is 16bits per channel. At least Photoshop and identify both claim that. The problem is that it doesn't look like it. It looks exactly like it's been truncated to 8bits per channel and then saved as 16bits per channel.
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fmw42
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

Does this look OK to you? It displays fine in Mac PREVIEW but is darker in IM display.

Code: Select all

montage cropped_spherical-lighting-test1.+AA+000001.exr cropped_spherical-lighting-test1.+AA+000001.exr -geometry +0+0 -tile 2x1 tmp3.exr

identify -verbose tmp3.exr

Image: tmp3.exr
  Format: EXR (High Dynamic-range (HDR))
  Class: DirectClass
  Geometry: 200x200+0+0
  Units: Undefined
  Type: TrueColorAlpha
  Endianess: Undefined
  Colorspace: RGB
  Depth: 16-bit
  Channel depth:
    red: 15-bit
    green: 15-bit
    blue: 16-bit
    alpha: 1-bit
I think the issue is that EXR is a linear format. Some viewers will honor the linear space (such as IM display), but others will assume sRGB. So convert the result to sRGB. This works for me.

Code: Select all

convert tmp3.exr -colorspace sRGB tmp4.exr

display tmp4.exr

See http://www.imagemagick.org/script/formats.php

"A majority of the image formats assume an sRGB colorspace (e.g. JPEG, PNG, etc.). A few support only linear RGB (e.g. EXR, DPX, CIN, HDR) "


P.S. Seems like montage does honor -colorspace sRGB, so just try

Code: Select all

montage cropped_spherical-lighting-test1.+AA+000001.exr cropped_spherical-lighting-test1.+AA+000001.exr -geometry +0+0 -tile 2x1 -colorspace sRGB tmp5.exr

display tmp5.exr
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digitalis99
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

I've tinkered with a few options for montage, per your prompting. I've tried "-colorspace RGB", "-colorspace sRGB", "-define exr:color-type=RGB", "-define exr:color-type=sRGB"...none of which made any difference. If you look at an "identify -verbose" pass on the cropped tile with CD in the name, you get this:

Code: Select all

  Channel statistics:
    Pixels: 20000
    Red:
      min: 3901.94 (0.0595398)
      max: 1.#INF (1.#INF)
      mean: 1.#INF (1.#INF)
      standard deviation: -1.#IND (-1.#IND)
      kurtosis: -1.#IND
      skewness: -1.#IND
      entropy: 0.607496
    Green:
      min: 5423.92 (0.0827637)
      max: 1.#INF (1.#INF)
      mean: 1.#INF (1.#INF)
      standard deviation: -1.#IND (-1.#IND)
      kurtosis: -1.#IND
      skewness: -1.#IND
      entropy: 0.604619
Notice the Max value is, I assume, clipped in both cases. If you run an "identify -verbose" on the correct output file, you'll see the same thing as regards the max value for both the red and green channels, with a minimum value on the red channel being 768.488 and minimum for green at 451.493.

To the contrary, if you run "identify -verbose" on the stitched result from montage, you get this:

Code: Select all

  Channel statistics:
    Pixels: 2000000
    Red:
      min: 593.991 (0.00906372)
      max: 65535 (1)
      mean: 25044.3 (0.382152)
      standard deviation: 16765.5 (0.255825)
      kurtosis: -0.241287
      skewness: 0.865055
      entropy: 0.921521
    Green:
      min: 384.494 (0.005867)
      max: 65535 (1)
      mean: 26097.7 (0.398226)
      standard deviation: 14740.1 (0.22492)
      kurtosis: 1.25858
      skewness: 1.34038
      entropy: 0.883645
Notice the minimum value for both the red and green channels went down, and the maximum dropped to be not clipped at the 16bit highest possible value of 65,535.

So, it appears montage is shifting the dynamic range of the image to avoid clipping. I can understand its desire to do so, but it causes unexpected results in this case. Is there a way to tell montage not to adjust the dynamic range to avoid clipping? I see -clamp, but it doesn't appear to have a "no" option.
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fmw42
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

On IM 6.9.2.6 Q16 (non-HDRI) Mac OSX for your image with CD in the name (cropped_spherical-lighting-test1.+CD+000001.exr), I do not get your odd results. (probably due to not using HDRI) I get

Code: Select all

Image: cropped_spherical-lighting-test1.+CD+000001.exr
  Format: EXR (High Dynamic-range (HDR))
  Class: DirectClass
  Geometry: 100x200+0+0
  Units: Undefined
  Type: TrueColorAlpha
  Endianess: Undefined
  Colorspace: RGB
  Depth: 16-bit
  Channel depth:
    red: 16-bit
    green: 16-bit
    blue: 16-bit
    alpha: 1-bit
  Channel statistics:
    Pixels: 20000
    Red:
      min: 4372 (0.0667124)
      max: 65535 (1)
      mean: 36465.7 (0.556431)
      standard deviation: 27618 (0.421424)
      kurtosis: -1.93906
      skewness: 0.0623597
      entropy: 0.606209
    Green:
      min: 6316 (0.096376)
      max: 65535 (1)
      mean: 39127.5 (0.597047)
      standard deviation: 25249.5 (0.385283)
      kurtosis: -1.91287
      skewness: 0.0353391
      entropy: 0.604285
    Blue:
      min: 90 (0.00137331)
      max: 1806 (0.0275578)
      mean: 717.733 (0.0109519)
      standard deviation: 507.952 (0.00775085)
      kurtosis: -0.858382
      skewness: 0.641439
      entropy: 0.956238
    Alpha:
      min: 65535 (1)
      max: 65535 (1)
      mean: 65535 (1)
      standard deviation: 0 (0)
      kurtosis: 0
      skewness: 0
      entropy: 0
  Image statistics:
    Overall:
      min: 0 (0)
      max: 65535 (1)
      mean: 19077.7 (0.291108)
      standard deviation: 18712 (0.285526)
      kurtosis: 6.41528
      skewness: 3.05981
      entropy: 0.541683
  Rendering intent: Undefined
  Gamma: 1
  Background color: rgba(255,255,255,1)
  Border color: rgba(223,223,223,1)
  Matte color: rgba(189,189,189,1)
  Transparent color: rgba(0,0,0,0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 100x200+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
    date:create: 2015-11-17T11:30:56-08:00
    date:modify: 2015-11-16T12:58:12-08:00
    signature: 94d34c29143d9c7f10b46e7736065bffc16521067fb21a3b748f52ee7aa19ad0
  Artifacts:
    filename: cropped_spherical-lighting-test1.+CD+000001.exr
    verbose: true
  Tainted: False
  Filesize: 164KB
  Number pixels: 20K
  Pixels per second: 2.5GB
  User time: 0.000u
  Elapsed time: 0:01.000
  Version: ImageMagick 6.9.2-6 Q16 x86_64 2015-11-14 http://www.imagemagick.org
With IM 6.9.1.10 HDRI, I do get your bad results

Code: Select all

im69110hdri identify -verbose cropped_spherical-lighting-test1.+CD+000001.exr
Image: cropped_spherical-lighting-test1.+CD+000001.exr
  Format: EXR (High Dynamic-range (HDR))
  Class: DirectClass
  Geometry: 100x200+0+0
  Units: Undefined
  Type: TrueColorAlpha
  Endianess: Undefined
  Colorspace: RGB
  Depth: 16-bit
  Channel depth:
    red: 16-bit
    green: 16-bit
    blue: 16-bit
    alpha: 1-bit
  Channel statistics:
    Pixels: 20000
    Red:
      min: 4371.93 (0.0667114)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.606209
    Green:
      min: 6315.9 (0.0963745)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.604285
    Blue:
      min: 89.6861 (0.00136852)
      max: 1805.97 (0.0275574)
      mean: 717.827 (0.0109533)
      standard deviation: 507.917 (0.00775031)
      kurtosis: -0.858658
      skewness: 0.641152
      entropy: 0.956238
    Alpha:
      min: 65535 (1)
      max: 65535 (1)
      mean: 65535 (1)
      standard deviation: 0 (0)
      kurtosis: 0
      skewness: 0
      entropy: 0
  Image statistics:
    Overall:
      min: 0 (0)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.541683
  Rendering intent: Undefined
  Gamma: 1
  Background color: rgba(255,255,255,1)
  Border color: rgba(223,223,223,1)
  Matte color: rgba(189,189,189,1)
  Transparent color: rgba(0,0,0,0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 100x200+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
    date:create: 2015-11-17T11:43:56-08:00
    date:modify: 2015-11-16T12:58:12-08:00
    signature: 94d34c29143d9c7f10b46e7736065bffc16521067fb21a3b748f52ee7aa19ad0
  Artifacts:
    filename: cropped_spherical-lighting-test1.+CD+000001.exr
    verbose: true
  Tainted: False
  Filesize: 164KB
  Number pixels: 20K
  Pixels per second: 4GB
  User time: 0.000u
  Elapsed time: 0:01.000
  Version: ImageMagick 6.9.1-10 Q16 x86_64 2015-07-25 http://www.imagemagick.org
Likewise, when using IM 6.9.2.6 Q16 HDRI, I get your same odd results with inf and nan showing in the channel stats.

Code: Select all

 im6926hdri identify -verbose cropped_spherical-lighting-test1.+CD+000001.exr
Image: cropped_spherical-lighting-test1.+CD+000001.exr
  Format: EXR (High Dynamic-range (HDR))
  Class: DirectClass
  Geometry: 100x200+0+0
  Units: Undefined
  Type: TrueColorAlpha
  Endianess: Undefined
  Colorspace: RGB
  Depth: 16-bit
  Channel depth:
    red: 16-bit
    green: 16-bit
    blue: 16-bit
    alpha: 1-bit
  Channel statistics:
    Pixels: 20000
    Red:
      min: 4371.93 (0.0667114)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.606209
    Green:
      min: 6315.9 (0.0963745)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.604285
    Blue:
      min: 89.6861 (0.00136852)
      max: 1805.97 (0.0275574)
      mean: 717.827 (0.0109533)
      standard deviation: 507.917 (0.00775031)
      kurtosis: -0.858658
      skewness: 0.641152
      entropy: 0.956238
    Alpha:
      min: 65535 (1)
      max: 65535 (1)
      mean: 65535 (1)
      standard deviation: 0 (0)
      kurtosis: 0
      skewness: 0
      entropy: 0
  Image statistics:
    Overall:
      min: 0 (0)
      max: inf (inf)
      mean: inf (inf)
      standard deviation: nan (nan)
      kurtosis: nan
      skewness: nan
      entropy: 0.541683
  Rendering intent: Undefined
  Gamma: 1
  Background color: rgba(255,255,255,1)
  Border color: rgba(223,223,223,1)
  Matte color: rgba(189,189,189,1)
  Transparent color: rgba(0,0,0,0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 100x200+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
    date:create: 2015-11-17T11:43:56-08:00
    date:modify: 2015-11-16T12:58:12-08:00
    signature: 94d34c29143d9c7f10b46e7736065bffc16521067fb21a3b748f52ee7aa19ad0
  Artifacts:
    filename: cropped_spherical-lighting-test1.+CD+000001.exr
    verbose: true
  Tainted: False
  Filesize: 164KB
  Number pixels: 20K
  Pixels per second: 2.5GB
  User time: 0.000u
  Elapsed time: 0:01.000
  Version: ImageMagick 6.9.2-6 Q16 x86_64 2015-11-17 http://www.imagemagick.org
You might post a note to the Bugs forum and reference back here. I do not know if this is an IM issue or one with your EXR files, but the IM developers should take a look. I believe that IM only permits the use of EXR "Half" format. Are your images Half or Full format EXR?
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fmw42
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

I think you have at least one bad image. I do not get the same inf and nan for other of your images. For example:

Code: Select all

im6926hdri idv cropped_spherical-lighting-test1.+AA+000001.exr
Image: cropped_spherical-lighting-test1.+AA+000001.exr
  Format: EXR (High Dynamic-range (HDR))
  Class: DirectClass
  Geometry: 100x200+0+0
  Units: Undefined
  Type: TrueColorAlpha
  Endianess: Undefined
  Colorspace: RGB
  Depth: 16-bit
  Channel depth:
    red: 16-bit
    green: 16-bit
    blue: 16-bit
    alpha: 1-bit
  Channel statistics:
    Pixels: 20000
    Red:
      min: 4751.93 (0.0725098)
      max: 13423.8 (0.204834)
      mean: 11070.8 (0.16893)
      standard deviation: 926.577 (0.0141387)
      kurtosis: -0.143403
      skewness: 0.460611
      entropy: 0.933098
    Green:
      min: 7699.88 (0.117493)
      max: 20751.7 (0.31665)
      mean: 17627.7 (0.268981)
      standard deviation: 1283.47 (0.0195846)
      kurtosis: 0.229231
      skewness: 0.414506
      entropy: 0.914077
    Blue:
      min: 128.748 (0.00196457)
      max: 328.995 (0.00502014)
      mean: 288.123 (0.00439647)
      standard deviation: 17.0209 (0.000259723)
      kurtosis: 1.29967
      skewness: 0.303937
      entropy: 0.819898
    Alpha:
      min: 65535 (1)
      max: 65535 (1)
      mean: 65535 (1)
      standard deviation: 0 (0)
      kurtosis: 0
      skewness: 0
      entropy: 0
  Image statistics:
    Overall:
      min: 0 (0)
      max: 20751.7 (0.31665)
      mean: 7246.65 (0.110577)
      standard deviation: 791.54 (0.0120781)
      kurtosis: 11539
      skewness: 261.905
      entropy: 0.666768
  Rendering intent: Undefined
  Gamma: 1
  Background color: rgba(255,255,255,1)
  Border color: rgba(223,223,223,1)
  Matte color: rgba(189,189,189,1)
  Transparent color: rgba(0,0,0,0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 100x200+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
    date:create: 2015-11-17T11:44:01-08:00
    date:modify: 2015-11-16T12:58:08-08:00
    signature: 9d45958318007b66bfda02cf6efb37e932cdcff1214ea4145794ccddef0ac0bc
  Artifacts:
    filename: cropped_spherical-lighting-test1.+AA+000001.exr
    verbose: true
  Tainted: False
  Filesize: 164KB
  Number pixels: 20K
  Pixels per second: 10GB
  User time: 0.000u
  Elapsed time: 0:01.000
  Version: ImageMagick 6.9.2-6 Q16 x86_64 2015-11-17 http://www.imagemagick.org
Fred-Weinhauss-Mac-mini:desktop fred$
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digitalis99
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

fmw42 wrote:I think you have at least one bad image. I do not get the same inf and nan for other of your images. For example:
The image was created by the render app that way. There is a "sun" present on that tile that shows exactly where the clipping is. There is no sun elsewhere on the image, so there shouldn't be clipping on any of the other tiles.

I'll post over on bugs and see where we go.
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

The post on the bugs forum has gone all of nowhere so far. I would have thought it would be taken at least somewhat seriously due to it being easily reproducible with the files I provided. The nature of the flaw is objectively obvious. Anyone?
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fmw42
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

Just a suggestion. Try using convert ... +-append to combine your images to see if convert has the same issue as montage. See http://www.imagemagick.org/Usage/layers/#append.
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

Convert doesn't have the same issue as montage, since I use convert to crop each output tile to only the portion of the image with information prior to using montage. I may have to resort to using convert, though, if none of the devs care about making montage work correctly.
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magick
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Re: Montage not maintaining 16 bit depth

Post by magick »

Montage places its image tiles on a canvas with a compositing operation, the default is 'over'. Compositing is governed by the SVG standard for alpha compositing which requires clamping for the 'over' operator. Try instead, the 'copy' op with '-compose copy' on your command-line. You may also need to use an HDRI-enabled version of ImageMagick to get the expected results.
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Re: Montage not maintaining 16 bit depth

Post by fmw42 »

Magick:

Would montage accept the -define compose:clamp=on|off (available as of 6.9.1-3)?
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magick
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Re: Montage not maintaining 16 bit depth

Post by magick »

Yes.
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Re: Montage not maintaining 16 bit depth

Post by digitalis99 »

Yea! That works as expected. I'm not so sure the default of that should be "over", but I'm happy to have that solved. Too bad it took so long to find. :^)
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