![]() It's funny that the function y(x) ) = y0+ (y1 - y0) (x - k g(x) ) uses just k=1, which doesn't have Not linear over the x-coordinate, but almost linear with an enlarged contrast by a polynomial So far it could be clarified how Photoshop constructs a gradient in RGB: So far I've not been able to work out an exact mapping that fits the black to white gradient and the 3 colours above. I tried the same in a linear gamma and got similar results. Instead I got a distinct S curve ( some sample values shown below) I expected this to be either one to one mapping of the L values or something that would explain the mapping above. Put a gradient map adjustment layer above it mapping to the same black to white range. So my next test was to create a black and white gradient using a Gradient Fill layer. So I also looked at the L values (I used sRGB for testing) The original posters question led from unexpected results when converting three colours to a gradient map adjustment layer set black to white. Your test was interesting and got me to do some more thinking. Not all gradients have the same hue or its equivalent in Lab, the same ratio a:b. *) Choosing colors sorted by L instead of linearly interpolating in Lab is for me not understandable. Where linear means a straight line in the respective color space with equidistant interpolation. Or last but not least linear in XYZ, which would be physically reasonable. In R', G', B' ( Gamma encoded) or linear in L of Lab*) or linear in Lab, or linear in HSB (HSL,HLS) There are many possibilities, linear in R, G, B or linear The gradient is visually far from being perfect: we have almost equal lightnesses in the three G and B are not linear with gamma encoding taken into account (center is at 127/128)ĥ. The distance x=0.0 to 1.0 is divided linearly.Ģ. Let's have a look at a gradient test image, made by Photoshop CS6 in sRGB:ġ. Home | Glossary | Notation | Links | References | CalculatorsĬontact Us to ask a question, provide feedback, or report a problem.For me the explanations are not convincing, so far. Gradient Estimate Between Piezometers (screen lengths equal to zero) The well is dry and no calculation is performed. The gradient is calculated from the mid-point of the water level and the bottom of the well screen. The well screen intersects the water-table. ![]() The water level is above the top of the well screen. There are three possibilities for how the water levels relate to the well screen: A separate version of the calculator gives these values more explicitly. These values are calculated from varying assumptions about the influence of the well screen. Because there are other options, an estimate of the range of possible gradients is given in the output. One choice is to use the mid-points of the well screens to calculate the gradients (as illustrated). The change of head (roughly water level) divided by the distance determines the direction of flow. Where q is the Darcy flux (volume of water per unit area per unit time) and K is the hydraulic conductivity. ![]() Water levels in nested well clusters (wells located closely together) indicate upward or downward flow in aquifers or flow between adjacent geologic units. ![]() EPA On-line Tools for Site Assessment Calculation Module Home Objectives Table of Contents Previous ![]()
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