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doc:appunti:hardware:canoscan_9000f_mark_ii [2014/11/18 21:27] – [Invert and color balance] niccolodoc:appunti:hardware:canoscan_9000f_mark_ii [2018/01/04 11:57] – [Web references] niccolo
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 </code> </code>
  
-We choose by visual inspection the best value for gamma, 0.007 in this example.+We choose by visual inspection the best value for gamma; 0.007 in this example.
  
-The we open with Gimp a sample photo, we need a shot with a good **black**, **gray** and **white** spots. The process is:+Thake a film strip (negated and gamma-corrected with the above recipe) and open it with the Gimp. We need a strip with good **black**, **gray** and **white** spots. The process is:
  
   - Apply a **pixelize blur filter** on the black, gray and white spots. Make it large enough so you can easly pick the color from it in the next steps.   - Apply a **pixelize blur filter** on the black, gray and white spots. Make it large enough so you can easly pick the color from it in the next steps.
   - Open menu **//Colors//**, **//Levels//**:   - Open menu **//Colors//**, **//Levels//**:
     - From **//All Channels//**, click **//Pick gray point//** and then click on the gray spot.     - From **//All Channels//**, click **//Pick gray point//** and then click on the gray spot.
-    - From //Channel// select //Red//, click **//Pick black point//** and click on the black spot. Click **//Pick white point//** and click on the white spot.+    - From **//Channel//** select **//Red//**, click **//Pick black point//** and click on the black spot. Click **//Pick white point//** and click on the white spot.
     - Repeat the above step for **//Red//**, **//Green//** and **//Blue//**.     - Repeat the above step for **//Red//**, **//Green//** and **//Blue//**.
-  - Annotate the value of **black point**, **gamma**, and **white point** for each RGB channel.+  - Before closing the dialog box, annotate the values of **black point**, **gamma**, and **white point** for each RGB channel.
  
-Suppose that the values read from Gimp are:+Suppose that the values are:
  
-| Red    |  22 |  1.06 |  193 | +^ Channel  ^ Black  ^ Gamma  ^ White  ^ 
-| Green  |  20 |  1.01 |  190 | +| Red      |     22 |   1.06 |    193 | 
-| Blue   |  30 |  0.78 |  197 |+| Green    |     20 |   1.01 |    190 | 
 +| Blue     |     30 |   0.78 |    197 |
  
 The black and white points are integers 0-255, we need to convert it into a percent value; e.g. for the red white point: 22 / 255 * 100 = 8.63%. The black and white points are integers 0-255, we need to convert it into a percent value; e.g. for the red white point: 22 / 255 * 100 = 8.63%.
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   - Repeat the last two steps.   - Repeat the last two steps.
  
 +
 +===== ImageMagick convert, memory issue =====
 +
 +Executing **convert** on very large images can lead to memory exhausted issue. I experienced it converting a TIF scan into PNG (because I wish to avoid 24 bit Gimp limitation with TIF images):
 +
 +<code>
 +convert very-big.tif very-big.png
 +convert-im6.q16: DistributedPixelCache '127.0.0.1' @ error/distribute-cache.c/ConnectPixelCacheServer/244.
 +convert-im6.q16: cache resources exhausted `very-big.png' @ error/cache.c/OpenPixelCache/3945.
 +convert-im6.q16: No IDATs written into file `very-big.png' @ error/png.c/MagickPNGErrorHandler/1628.
 +</code>
 +
 +It seems that ImageMagick is self-limiting the disk resource it will use, you can fix the configuration file **''/etc/ImageMagick-6/policy.xml''**, increasing the **1GiB** limit:
 +
 +<code xml>
 +<policymap>
 +  <policy domain="resource" name="memory" value="256MiB"/>
 +  <policy domain="resource" name="map" value="512MiB"/>
 +  <policy domain="resource" name="width" value="16KP"/>
 +  <policy domain="resource" name="height" value="16KP"/>
 +  <policy domain="resource" name="area" value="128MB"/>
 +  <policy domain="resource" name="disk" value="1GiB"/>
 +</policymap>
 +</code>
 +
 +May be you can also increase the Memory resource, if you have enough:
 +
 +<code>
 +convert -list resource
 +Resource limits:
 +  Width: 16KP
 +  Height: 16KP
 +  Area: 128MP
 +  Memory: 256MiB
 +  Map: 512MiB
 +  Disk: 1GiB
 +  File: 768
 +  Thread: 2
 +  Throttle: 0
 +  Time: unlimited
 +</code>
  
 ===== Web references ===== ===== Web references =====
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   * [[http://125px.com/articles/photography/digital/colorneg/|Thoughts on Color Negative Scanning]]   * [[http://125px.com/articles/photography/digital/colorneg/|Thoughts on Color Negative Scanning]]
   * [[https://sites.google.com/site/negfix/|Negfix8 scrip]] to turn scanned negative image into the positive image.   * [[https://sites.google.com/site/negfix/|Negfix8 scrip]] to turn scanned negative image into the positive image.
 +  * [[https://zephyrsoft.org/blog/34-digitize-slides-and-prints-on-linux|Use Canon CanoScan 9000F Mark II to digitize slides and prints on Linux]], with some useful tips about doing crop and trim with Imagemagick, etc.
doc/appunti/hardware/canoscan_9000f_mark_ii.txt · Last modified: 2019/12/23 09:36 by niccolo