Timeline for How to measure an image's contrast?
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 13, 2016 at 10:48 | vote | accept | Élio Pereira | ||
| Mar 13, 2016 at 5:05 | comment | added | CuriousOne | The way Apple calibrates their screens is different from the way it's being done on PCs and if you use the color picker tool, it gives you multiple choices. One can pick the "native values", "srgb", "generic rgb" or "Adobe rgb". Moreover, I can calibrate my screen both on the Mac and the PC with a large number of options to optimize color reproduction. The same is true for digital cameras which sometimes have a dozen or more image calibration constants. There is not "one" way of encoding an image and every time you transcode for a different format you are likely to encounter another one. | |
| Mar 13, 2016 at 4:45 | comment | added | Count Iblis | This allows you to deduce the transform to linear colorspace that will make the brightness profiles across blurred high contrast areas satisfy the scaling relations that they should satisfy. | |
| Mar 13, 2016 at 4:42 | comment | added | Count Iblis | @CuriousOne In principle any arbitrary conversion could have been used, but if the image was meant to be displayed on a computer screen then it is quite likely that it had been converted to sRGB. Given some arbitrary nonlinear transform, you can attempt to find the transform back to linear colorspace by considering out of focus areas of the picture. Some high contrast transition from brightness v1 to v2 will due to blurring be displayed as a brightness profile that changes from v1 to v2 gradually. In linear colorspace these functions from different areas are related via a scaling transform. | |
| Mar 13, 2016 at 0:59 | comment | added | CuriousOne | Why would you pick this particular conversion? You don't know how the image file was created, neither does the OP, so there is no way to reconstruct the actual physical contrast from the image data. | |
| Mar 12, 2016 at 22:35 | history | answered | Count Iblis | CC BY-SA 3.0 |