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isp:vibrancy [2023/09/05 05:47] – [Possible optimization] Igor Yefmov | isp:vibrancy [2023/09/05 05:54] – [RGB color space] Igor Yefmov |
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Having said that we still want to make a distinction between "changing color's Saturation" and "changing color's Vibrancy" when talking about color corrections of a given image. Both increase the color's [[https://en.wikipedia.org/wiki/Colorfulness#Saturation|Saturation]] but one behaves like a linear Gain increase, applied uniformly to any color. And the other one uses a sliding scale that adjusts the magnitude of change based on the current Saturation level, where the highest multiplication is done for low Saturation colors and highly vibrant (highly saturated, vivid) colors are adjusted on a progressively smaller scale. | Having said that we still want to make a distinction between "changing color's Saturation" and "changing color's Vibrancy" when talking about color corrections of a given image. Both increase the color's [[https://en.wikipedia.org/wiki/Colorfulness#Saturation|Saturation]] but one behaves like a linear Gain increase, applied uniformly to any color. And the other one uses a sliding scale that adjusts the magnitude of change based on the current Saturation level, where the highest multiplication is done for low Saturation colors and highly vibrant (highly saturated, vivid) colors are adjusted on a progressively smaller scale. |
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===== Implementation overview (YUV color space) ===== | ===== RGB color space ===== |
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| ===== YUV color space ===== |
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The goal is to increase the Saturation of each pixel based on its current Saturation level, where the increase factor is inversely proportional to the current value. Given the range of values for ''U'' and ''V'' \(\in[-127..+128]\), the highest increase factor will be around values of ''0'' and as the value gradually nears either end of the spectrum the multiplication coefficient approaches \(1.0\). | The goal is to increase the Saturation of each pixel based on its current Saturation level, where the increase factor is inversely proportional to the current value. Given the range of values for ''U'' and ''V'' \(\in[-127..+128]\), the highest increase factor will be around values of ''0'' and as the value gradually nears either end of the spectrum the multiplication coefficient approaches \(1.0\). |
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===== Implementation overview (HSL color space) ===== | ===== HSL color space ===== |
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Moving to HSL for image processing has a wonderful advantage of "separation of concerns" where the 3 visual components are treated independently of each other. Correcting the Saturation is just one of such areas where moving into HSL color space provides a notable simplification in the approach. As the \(S\) component of the HSL is "just" a linear scalar value we don't need to concern ourselves with the ''UV'' square or an ''RGB'' cube and just directly approach the subject of calculating only the \(S\). | Moving to HSL for image processing has a wonderful advantage of "separation of concerns" where the 3 visual components are treated independently of each other. Correcting the Saturation is just one of such areas where moving into HSL color space provides a notable simplification in the approach. As the \(S\) component of the HSL is "just" a linear scalar value we don't need to concern ourselves with the ''UV'' square or an ''RGB'' cube and just directly approach the subject of calculating only the \(S\). |