Issues converting to 8bit Tif

[rossoe]

I have an application that requires input of 8bit lzw compressed tif files

the original images are 'bmp's' and are fairly large 40960 x 40960 - (aerial photography)

So handling them in Photoshop was not possible as a single image, I splice them into 4 tiles or 20480.

I needed to convert these 4 bmp's into tif's and then stitch them back into a single image.

It seemed faster for me to convert to tif in PS, so I then had 4 tif's which were showing as 8bit

I then used combo of the following commands to stitch back into one image:

Code: Select all

magick convert -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb *.tif +append output.tif

magick convert -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb *.tif -append output.tif

so I had a nice single image - I ran an 'identify' command which seemed to show 8bit depth:

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E:\test\8bit\Final>magick identify -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb -verbose iow_8bit.tif
load image[iow_8bit.tif]: 40959 of 40960, 100% complete
Image: iow_8bit.tif
  Format: TIFF (Tagged Image File Format)
  Mime type: image/tiff
  Class: DirectClass
  Geometry: 40960x40960+0+0
  Resolution: 72x72
  Print size: 568.889x568.889
  Units: PixelsPerInch
  Type: Palette
  Base type: TrueColor
  Endianess: LSB
  Colorspace: sRGB
  Depth:[b] 8-bit[/b]
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit
 Transparent color: none
 Interlace: None
 Intensity: Undefined
 Compose: Over
 Page geometry: 40960x40960+0+0
 Dispose: Undefined
 Iterations: 0

 Compression: LZW

I could not check the properties of the image in explorer as it did not seem to hold any info?

but double checking in irfanview showed it was still:
16,7 Million (24 BitsPerPixel)

So I ended up just using irfanview to decrease colour depth to 256, and it was then in the right 8bit format.

I would like to know what I'm doing wrong in Imagemagick? as my 4 x 8bit tif's are suddenly turning back to 24bit when stitching into a single image!

[snibgo]

I'm not clear what you want, or what the problem is. From identify, you have 3 channels. If they are 8 bits/channel, that is 24 bits/pixel in total.

Do you want palette files, that are 8 bits per pixel total? Then use "-type palette".

[rossoe]

So here are the 'identify' details on the 4 images before I stitch them together with ImageMagick:

iow_1x1m_8bit.tif

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Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8/1-bit
  Channel depth:
    Red: 1-bit
    Green: 1-bit
    Blue: 1-bit

iow_1x2m_8bit.tif

Code: Select all

Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8/1-bit
  Channel depth:
    Red: 1-bit
    Green: 1-bit
    Blue: 1-bit

iow_2x1m_8bit.tif

Code: Select all

Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit

iow_2x2m_8bit.tif

Code: Select all

Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8/1-bit
  Channel depth:
    Red: 1-bit
    Green: 1-bit
    Blue: 1-bit

The resulting single image is coming out as:

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  Type: Palette
  Base type: TrueColor
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit

"Base type: TrueColor" comes into play?

So are you saying I need to add the "-type palette" flag within my append type commands:

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magick convert -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb *.tif +append output.tif

[snibgo]

Your four input images have palettes. Your output also has a palette.

Isn't that what you want? Please say what problem you want to solve.

[rossoe]

Even though the identify is showing "Depth: 8-bit", when I checked the final single image in irfanview it said it was back to 24bit
https://imgur.com/a/RnPab

I needed the final single image to be 8bit

So I had to decrease colour depth in irfanview to get it back to 8bit again
https://imgur.com/a/RnPab

But I would rather be able to do the whole process in imagemagick.

[snibgo]

I repeat:

Do you want palette files, that are 8 bits per pixel total? Then use "-type palette".

Does that do what you want?

[rossoe]

I'm after 8bit (indexed colour - 256 colours)

Type: Palette
Base type: TrueColor < **** does this mean that it's 24 bit? *****
Endianess: LSB
Colorspace: sRGB
Depth: 8-bit < ** regardless of this **
Channel depth:
Red: 8-bit
Green: 8-bit
Blue: 1-bit

I ran this command on all my append's:

magick convert -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb *.tif +append -type palette -depth 8 output1.tif

and I end up with a single image with these properties:

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Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 2/8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit

Explorer see's it as 4bit

Irfanview see's it as this:
https://imgur.com/a/jYFDY

Does this look right?

[snibgo]

So you care about how the file is stored. Is that right? You want that to be paletted.

Don't ask IM how the file is stored. IM won't tell you. IM will tell you about the image (not the file) after the image has been read into memory.

exiftool will tell you about the file. Other tools might also.

[rossoe]

Thank you for your help on this snibgo by the way, i apologise as I am not familiar with image bit depth and colour profiles
I have been trying to read up on it here:
https://books.google.co.uk/books?id=6KV ... on&f=false

So I tested stitching together using commands which now includes the "-type palette"
example:

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magick convert -monitor -define registry:temporary-path=E:\Windows\Temp -limit memory 16mb *.tif +append -type palette output4.tif

The result was a single file with these details:

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Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 2/8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit

This failed to work in the application which appears to be fussy re input image.

Comparing the image that does work in the application -
which was 'reduced to 256 colours' using irfanview it has these properties:

Code: Select all

 Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 8-bit

I've progressed in terms of the final image not jumping back to 24 bit because I've added in the -type palette variable.

Am i able to enforce particular channel depth (blue) to match working example above?

what does the Depth: 2/8-bit actually mean?

[snibgo]

what does the Depth: 2/8-bit actually mean?

It means that after ImageMagick has read the image, by one measure the pixels need only 2 bits, and by another they need 8 bits. I forget the details of the measures. You can see that IM has figured the red and green channels need 8 bits but the blue channel needs only 1 bit.

The colormap (later in the "identify -verbose" listing) may provide clues.

[rossoe]

Ok so I ran a 'identify' on both, could you please help me check what it so different which I might be able to fix with a revised command -

seems like my application is happy with a tif when the colormap is buffered out to 256 colours? - but are you able to preserve that from the source tif's?

The 4 images that are stitched together to make the final working one below, are also showing the buffered out 256 colours (They were converted in Photoshop to 'indexed colour').

image that is working in application:

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Image: iow_8bitreal.tif
  Format: TIFF (Tagged Image File Format)
  Mime type: image/tiff
  Class: PseudoClass
  Geometry: 40960x40960+0+0
  Resolution: 72x72
  Print size: 568.889x568.889
  Units: PixelsPerInch
  Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 8-bit
  Channel statistics:
    Pixels: 1677721600
    Red:
      min: 1 (0.00392157)
      max: 207 (0.811765)
      mean: 1.32585 (0.0051994)
      standard deviation: 8.13319 (0.0318949)
      kurtosis: 631.4
      skewness: 25.1291
      entropy: 0.0113728
    Green:
      min: 1 (0.00392157)
      max: 255 (1)
      mean: 59.5293 (0.233448)
      standard deviation: 106.842 (0.418989)
      kurtosis: -0.356985
      skewness: 1.2806
      entropy: 0.397466
    Blue:
      min: 1 (0.00392157)
      max: 255 (1)
      mean: 196.235 (0.769548)
      standard deviation: 107.112 (0.420048)
      kurtosis: -0.376726
      skewness: -1.27408
      entropy: 0.780374
  Image statistics:
    Overall:
      min: 1 (0.00392157)
      max: 255 (1)
      mean: 85.6966 (0.336065)
      standard deviation: 119.689 (0.469368)
      kurtosis: -1.50008
      skewness: 0.706396
      entropy: 0.297303
  Compute image colors...  [iow_8bitreal.tif]: 40959 of 40960, 100% complete
  Colors: 4
  Histogram:
  Compute image colors...  [iow_8bitreal.tif]: 40959 of 40960, 100% complete
1289564662: (  1,  1,255) #0101FF srgb(1,1,255)
 385407459: (  1,255,  1) #01FF01 srgb(1,255,1) 4, 00% complete
    149340: ( 75, 41,  1) #4B2901 srgb(75,41,1)
   2600139: (207,115,  1) #CF7301 srgb(207,115,1)
compute image histogram[iow_8bitreal.tif]: 3 of 4, 100% complete
  Colormap entries: 256
  Colormap:
         0: ( 75, 41,  1,255) #4B2901FF srgba(75,41,1,1)
         1: (  1,255,  1,255) #01FF01FF srgba(1,255,1,1)
         2: (  1,  1,255,255) #0101FFFF srgba(1,1,255,1)
         3: (207,115,  1,255) #CF7301FF srgba(207,115,1,1)
         4: (  0,  0,  0,255) #000000FF black
         5: (  0,  0,  0,255) #000000FF black
         6: (  0,  0,  0,255) #000000FF black
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       229: (  0,  0,  0,255) #000000FF black
       230: (  0,  0,  0,255) #000000FF black
       231: (  0,  0,  0,255) #000000FF black
       232: (  0,  0,  0,255) #000000FF black
       233: (  0,  0,  0,255) #000000FF black
       234: (  0,  0,  0,255) #000000FF black
       235: (  0,  0,  0,255) #000000FF black
       236: (  0,  0,  0,255) #000000FF black
       237: (  0,  0,  0,255) #000000FF black
       238: (  0,  0,  0,255) #000000FF black
       239: (  0,  0,  0,255) #000000FF black
       240: (  0,  0,  0,255) #000000FF black
       241: (  0,  0,  0,255) #000000FF black
       242: (  0,  0,  0,255) #000000FF black
       243: (  0,  0,  0,255) #000000FF black
       244: (  0,  0,  0,255) #000000FF black
       245: (  0,  0,  0,255) #000000FF black
       246: (  0,  0,  0,255) #000000FF black
       247: (  0,  0,  0,255) #000000FF black
       248: (  0,  0,  0,255) #000000FF black
       249: (  0,  0,  0,255) #000000FF black
       250: (  0,  0,  0,255) #000000FF black
       251: (  0,  0,  0,255) #000000FF black
       252: (  0,  0,  0,255) #000000FF black
       253: (  0,  0,  0,255) #000000FF black
       254: (  0,  0,  0,255) #000000FF black
       255: (  0,  0,  0,255) #000000FF black
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Matte color: grey74
  Background color: white
  Border color: srgb(223,223,223)
  Transparent color: none
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 40960x40960+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: LZW
  Orientation: TopLeft
  Properties:
    date:create: 2018-01-19T07:36:13+00:00
    date:modify: 2018-01-19T07:36:18+00:00
    signature: 54c321aafeb789e8a45ddd0626be1d00288cd0a7d5ae7d8616a0d4a2e4b71726
    tiff:alpha: unspecified
    tiff:endian: lsb
    tiff:photometric: palette
    tiff:rows-per-strip: 1024
    tiff:software: IrfanView
  Artifacts:
    verbose: true
  Registry:
    temporary-path: E:\Windows\Temp
  Tainted: False
  Filesize: 2.15274MiB
  Number pixels: 1.67772G
  Pixels per second: 5098450B
  User time: 16.344u
  Elapsed time: 5:30.064
  Version: ImageMagick 7.0.6-3 Q16 x64 2017-07-24 http://www.imagemagick.org

Image that is not working in application:

Code: Select all

Image: output.tif
  Format: TIFF (Tagged Image File Format)
  Mime type: image/tiff
  Class: PseudoClass
  Geometry: 40960x40960+0+0
  Resolution: 72x72
  Print size: 568.889x568.889
  Units: PixelsPerInch
  Type: Palette
  Endianess: LSB
  Colorspace: sRGB
  Depth: 2/8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 1-bit
  Channel statistics:
    Pixels: 1677721600
    Red:
      min: 0 (0)
      max: 2 (0.811765)
      mean: 0.00385172 (0.00128391)
      standard deviation: 0.0961456 (0.0320485)
      kurtosis: 631.478
      skewness: 25.1308
      entropy: 0.0113728
    Green:
      min: 0 (0)
      max: 3 (1)
      mean: 0.691302 (0.230434)
      standard deviation: 1.26192 (0.42064)
      kurtosis: -0.357067
      skewness: 1.28057
      entropy: 0.397466
    Blue:
      min: 0 (0)
      max: 3 (1)
      mean: 2.30592 (0.76864)
      standard deviation: 1.26511 (0.421702)
      kurtosis: -0.376725
      skewness: -1.27408
      entropy: 0.780374
  Image statistics:
    Overall:
      min: 0 (0)
      max: 3 (1)
      mean: 1.00036 (0.333453)
      standard deviation: 1.41365 (0.471217)
      kurtosis: -1.5001
      skewness: 0.706386
      entropy: 0.297303
  Compute image colors...  [output.tif]: 40959 of 40960, 100% complete
  Colors: 4
  Histogram:
  Compute image colors...  [output.tif]: 40959 of 40960, 100% complete
1289564662: (  0,  0,255) #0000FF blue
 385407459: (  0,255,  0) #00FF00 lime of 4, 00% complete
    149340: ( 74, 41,  0) #4A2900 srgb(74,41,0)
   2600139: (207,115,  0) #CF7300 srgb(207,115,0)
compute image histogram[output.tif]: 3 of 4, 100% complete
  Colormap entries: 4
  Colormap:
         0: ( 74, 41,  0,255) #4A2900FF srgba(74,41,0,1)
         1: (207,115,  0,255) #CF7300FF srgba(207,115,0,1)
         2: (  0,255,  0,255) #00FF00FF lime
         3: (  0,  0,255,255) #0000FFFF blue
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Matte color: grey74
  Background color: white
  Border color: srgb(223,223,223)
  Transparent color: none
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 40960x40960+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: LZW
  Orientation: TopLeft
  Properties:
    date:create: 2018-01-21T19:16:27+00:00
    date:modify: 2018-01-21T19:22:08+00:00
    dc:format: image/tiff
    icc:copyright: Copyright (c) 1998 Hewlett-Packard Company
    icc:description: sRGB IEC61966-2.1
    icc:manufacturer: IEC http://www.iec.ch
    icc:model: IEC 61966-2.1 Default RGB colour space - sRGB
    photoshop:ColorMode: 2
    photoshop:ICCProfile: sRGB IEC61966-2.1
    signature: e80109e433df98d95a7c01cc7090290c7153813825664641ca9d337a1dcdbd55
    tiff:alpha: unspecified
    tiff:endian: lsb
    tiff:photometric: palette
    tiff:rows-per-strip: 40960
    xmp:CreateDate: 2017-03-12T00:08:01Z
    xmp:CreatorTool: Adobe Photoshop CS6 (Windows)
    xmp:MetadataDate: 2018-01-14T19:52:47Z
    xmp:ModifyDate: 2018-01-14T19:52:47Z
    xmpMM:DocumentID: xmp.did:497EBA65ECF7E711AF28BFB9A6A29B7F
    xmpMM:InstanceID: xmp.iid:7A25727E64F9E7118F5591A4DCCCE539
    xmpMM:OriginalDocumentID: xmp.did:497EBA65ECF7E711AF28BFB9A6A29B7F
  Profiles:
    Profile-8bim: 4418 bytes
    Profile-icc: 3144 bytes
    Profile-xmp: 15144 bytes
  Artifacts:
    verbose: true
  Registry:
    temporary-path: E:\Windows\Temp
  Tainted: False
  Filesize: 821062B
  Number pixels: 1.67772G
  Pixels per second: 5.06453MB
  User time: 17.859u
  Elapsed time: 5:32.268
  Version: ImageMagick 7.0.6-3 Q16 x64 2017-07-24 http://www.imagemagick.org

[snibgo]

As you can see, your images have only four colours. The "not working" version has a colormap (in memory) of only four entries, hence the "2 bits" for the depth: each pixel has only 2 bits, because that's all they need.

I don't think IM has a method to force the colormap (in memory or in file) to be larger than it needs to be.

What software is tying to read your "not working" image? You might report the problem to them.

[rossoe]

It's a custom built mod that runs on top of Arma 3 engine to manage surface masks https://forums.bohemia.net/forums/topic ... ap-makers/

It apparently uses the "Lossless Fast Pseudo-Quantization Algorithm" by Carsten Klein
https://sourceforge.net/p/freeimage/patches/99/

and they have it set so it's output is always an exported 8bit LZW TIF

On smaller images it can cope with converting 24bit down to 8bit itself, but because my image was much larger I discovered it could only cope if I input exactly 8bit (it's native export depth).

So the only current fix is reducing 256 colours via irfanview - My remaining query is why irfanview & Photoshop both add all that colourmap buffering not technically required? which imagemagick typically strips out.

if you look at the settings in irfanview:
https://imgur.com/a/RnPab
It does mention it's using - Floyd-Steinberg dithering (for max. 256 colours)

not sure if that is even relevant?

[snibgo]

As there is no colour reduction, dithering isn't relevant here.

Using a colormap of just four entries instead of 256 means the map is smaller, but more importantly only 2 bits are needed per pixel instead of 8. When you have 1.7G pixels, this is worth saving.

IrfanView can read 2-bit palette files and write them as 8-bit, so that seems a clean solution:

Code: Select all

i_view64.exe in.tif /convert=out.tif