doc:appunti:software:color_management
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doc:appunti:software:color_management [2019/12/27 10:03] – [The ColorChecker Chart] niccolo | doc:appunti:software:color_management [2022/08/08 16:30] (current) – [Other Interesting Pages] niccolo | ||
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To **convert** the stored **numerical values** back to **light intensity**, | To **convert** the stored **numerical values** back to **light intensity**, | ||
- | So the **sRGG** (non linear) color space is widely used; that model is often called **perceptual gamma**. But if you work with high quality images (**16 bits per channel**) and if you want to **apply filters** that work on light and shadow, you should use a linear (RBG) workspace. The **GIMP 2.10** program internally uses linear channels data when higher than 8-bit per channel precision is used. | + | So the **sRGB** (non linear) color space is widely used; that model is often called **perceptual gamma**. But if you work with high quality images (**16 bits per channel**) and if you want to **apply filters** that work on light and shadow, you should use a linear (RBG) workspace. The **GIMP 2.10** program internally uses linear channels data when higher than 8-bit per channel precision is used. |
* **[[https:// | * **[[https:// | ||
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===== The GIMP ===== | ===== The GIMP ===== | ||
- | The **GIMP** version **2.10** is required for **color management** and to handle images with **16 bit** per color channel. | + | The **GIMP** version **2.10** is required for **color management** and to handle |
{{.: | {{.: | ||
To view **CIE LAB** values in **Color Picker**: select the Color Picker tool, then keep the **shift key** pressed while clicking over the image. | To view **CIE LAB** values in **Color Picker**: select the Color Picker tool, then keep the **shift key** pressed while clicking over the image. | ||
- | ===== The ColorChecker Chart ===== | + | ===== Other Interesting Pages ===== |
- | The **[[wp> | + | * **[[colorchecker_clones]]** |
+ | * **[[imagemagick_color_management]]** | ||
+ | * **[[keldan_underwater_color_checker]]** | ||
- | The most inexpensive color charts are obtained by **[[wp> | ||
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- | {{.: | ||
- | {{.: | ||
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- | Having a **reference picture** of the ColorChecker can be very useful. A ColorChecker reference image can be used as a comparison with images acquired using a scanner or with photos taken in some light condition: just include the actual ColorChecker into the scan or into the photo and calculate the transformation functions to obtain the same color tones of the refrence picture with a suitable software (e.g. // | ||
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- | Surprisingly enough, it is not easy to find or to create such a picture. | ||
- | X-Rite publishes the document [[https:// | ||
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- | Beware that the above data refers to ColorChecker **manufactured before November 2014**, after that data some changes were introduced, perhaps due the necessity to comply with toxicity law in color pigments. For X-Rite ColorChecker manufactured after november 2014 there is the **{{.: | ||
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- | Another problem in creating ColorChecker images is the **poor support** for L*a*b* color space and 16 bit/color in image manipulation applications. Using the **GIMP** you need at least **version 2.10** to open 16 bit TIFF images; you will have a color picker that shows you color coordinates in **sRGB 16 bit integers** and **%%L*a*b* floating points%%**, but you are still limited to enter color coordinates using **0-255** or **0-100** ranges. | ||
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- | * **ColorChecker sRGB image Macbeth Lab**\\ Created from GretagMacbeth L*a*b* D50 data, for charts manufactured before Nov. 2014. | ||
- | * **ColorChecker sRGB image BabelColorAvg**\\ Created from BabelColor data, average of 30 charts manufactured before Nov. 2014. | ||
- | * **ColorChecker sRGB image X-Rite AfterNov2014**\\ Created from X-Rite L*a*b* D50 data, for chars manufactured after Nov. 2014. | ||
- | ===== Web References ===== | ||
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- | * **[[http:// | ||
- | * **{{.: | ||
- | * **{{.: | ||
- | * **{{.: |
doc/appunti/software/color_management.1577437388.txt.gz · Last modified: 2019/12/27 10:03 by niccolo