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POWhat's the formula to increase the luminance in an image in a similar way how the L component in Photoshop does it?
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copied!<p>For example I have a pixel with these values:</p> <pre><code>CGFloat red = 34 // 0 - 255 CGFloat green = 128 CGFloat blue = 190 </code></pre> <p>and I want to increase luminance so that blue is 255. NOTE: With "Luminance" I mean the L-component of Photoshop in LAB color space. See pictures!</p> <p>There must be a special formula to compute the RGB values for the increased luminance, because the R G B values are modified in a non-linear way!</p> <p>Proof: I did a test in Photoshop and created this same color, and then opened the color picker to examine it:</p> <p><img src="https://i.stack.imgur.com/0yQxv.png" alt="Original color"></p> <p>Then I activated the L component of the LAB color space, which controls luminance (at least that is what I am talking about - I mean the brightness controlled by that L component. Guess that is luminance).</p> <p>So with L activated, I dragged the slider on the left upwards until B reached 255: <img src="https://i.stack.imgur.com/XQDcq.png" alt="Modified color"></p> <p>Now read the resulting R G B values:</p> <pre><code>CGFloat newRed = 112 // 0 - 255 CGFloat newGreen = 188 CGFloat newBlue = 255 </code></pre> <p>The differences between these is:</p> <pre><code>newRed - red = +78 newGreen - green = +60 newBlue - blue = +65 </code></pre> <p>The percentages are:</p> <pre><code>red shift: +38.42% green shift: +29.55% blue shift: +32.01% </code></pre> <p>This does not correspond with the known formula for computing Luminance out of R G B, which is something close to <code>luminance = (red * 0.3) + (green * 0.6) + (blue * 0.1)</code>.</p> <p>Obviously, they have been shifted in a non-linear manner.</p> <p>Is there a known way to compute newRed, newGreen, newBlue out of red, green, blue in a similar fashion how Photoshop does it?</p>

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