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14

Yes, while many screens and OS operations are using a gamma of 2.2 your hardware and computation result still need to be corrected. There are also special mediums such as broadcast TV's that have a different gamma. Sensor equipment like cameras are mostly linear so they need to be adjusted accordingly. Besides this the user can set their system to whatever ...


12

What the video is talking about is called gamma correction and it's a very familiar topic for graphics programmers. The first 30 minutes of John Hable's talk on Uncharted 2 rendering is my favorite introduction to "why graphics programmers should care about gamma", as well as being a good introduction to HDR rendering. If you don't want to watch the talk (...


11

The de facto standard color space for digital images these days is sRGB. sRGB is a good default assumption if working with a display whose exact color space is not known (i.e. most random displays someone might run your app on), or images whose color space encoding is not known (i.e. most random image files you might encounter). The sRGB standard defines ...


10

We know that in PNG,BMP,etc... the pixel value stored is not in the linear RGB space. This is not necessarily true. You can store whatever color space you want into an image, it doesn't even need to be colors (such as normal maps). The alpha channel is generally linear. The alpha channel doesn't get displayed, but it is generally a non-color term used for ...


7

Yes, your theory is correct. A gamma-correct blur entails converting the input pixels to linear color space, performing the blur weighting and accumulation in that space, and then converting back to gamma space at the end. As noted in the comments, the actual transform is not literally squaring and square-rooting, that's just an approximation (and not that ...


6

Is every image from the internet commonly got gamma corrected? Every image is encoded with a color profile. Most color profiles do have a gamma correction, but not every color profile has that (raw for example). Most images on the internet are encoded in sRGB, which is gamma corrected. If you would download a random image from the internet, you will more ...


6

The short answer is "no", for reasons covered in Alvy Ray Smith's memo, Gamma Correction. Gamma is not about nonlinearity in human perception, it's about nonlinearity in display devices (and, I suppose, acquisition devices too).


6

If I get correctly what you are asking you basically just need to find the G in this equation: $$Image_{out} = Image_{in}^G$$ This could be easily solved as $$G = \frac{\log{Image_{out}}}{\log{Image_{in}}}$$ Because usually gamma is applied in a uniform fashion on the image, you can just pick any two non zero pixel values (one for source and one for ...


6

Short answer, set the precision of the image to a higher value. Long answer, When looking at a gamma correction curve, you can see that the lower values get changed much more, this means that the difference between lower values will get greater and that causes this effect. You have a limited amount of values for a color channel and this means that when it ...


5

The fact that a photo is stored in gamma space doesn't have to do with PNG or JPEG, it has to do with the fact that it's a photo. The camera detects a 50% intensity but is going to save it as a 187 instead of 127, because that is more efficient to keep the color information that matters to the human eye when you have only 256 different possible values. And ...


4

In short: You should not gamma correct your glow map. In fact, you should do everything in a linear color space. At the very end, when doing any color grading (which is the very last step), you convert the final image to the right color space. The color space include that gamma correction. In long: Gamma correction is a step in the encoding of images. It ...


3

This has to do with gamma correction. If one pixel has red component with value of 1 (where 255 is max), the next pixel has value for red that is 2, there no guarantee that exactly twice as much photons are exiting from the second pixel. Displays have different curves that predict what's the expected brightness. It also has to do with how our eyes work: ...


3

Introduction It depends on how you create the map! Consider the following and let it sink in for a while before you go forward: The image is displayed with a gamma correction for the benefit of your eyes The data is still just data. The gamma correction is for the display part not the data part. Now a bump map is pretty hard to draw with a paint ...


3

JPG, PNG or any other 8 bit image formats do not intrinsically have 1/2.2 gamma associated with it. They just store values from 0-255. How that data is interpreted depends on the software that reads and writes those files. The interesting fact is that most image editing software uses gamma color space by default. All the brushes, effects, filters and even ...


3

Actually, if your bump or displacement map is saved with that 0.45 gamma correction, it's wrong. These maps contain geometrical information rather than colour, and as such, should be simply encoded linearly. For a related issue and a fix for Adobe Photoshop, see this slide deck: https://docs.google.com/presentation/d/1vS5nAAnXbZ8Pt6-dXxy-...


3

Image file formats themselves do not regard the gamma but store pixel values unmodified as the authoring program (e.g. Photoshop) decides to store the values, so RGB and alpha channels have no distinction from image file format point of view (barring potential lossy compression strategies, but that's another topic). However, when you author images in ...


2

You can get fancy with individual weighting on the blur maps if you want to adjust the look, but an equally weighted mix (and yes, it should be additive) will work too. I’m not sure about whether you need to gamma-correct the blurred image before adding it to the source one, but you should definitely get it into linear space before doing the blur; this ...


2

According to Wikipedia (insert standard disclaimer RE accuracy): JPEG does not define which color encoding is to be used for images. JFIF defines the color model to be used: either Y for greyscale, or YCbCr as defined by CCIR 601. YCbCr is a non-linear format. As I mentioned earlier, "Video Demystified" states: "YCbCr is the color space originally ...


2

I have found the issue. The gamma correction was the correct value, the same as in the book (1/2), but the light source had the brightness of 1.0f. The book had set the light's brightness to 18.0f for all color channels. This would introduce color overflow if left at that, and the very light areas (above 1.0f, and subsequently when converted, outside the ...


1

Yes and no. The RGB values are most likely gamma compressed. Consider gamma calibration images like the one below. For a well calibrated monitor the gray value should look the same as the pattern of black and white lines. If you load in the image you will likely find RGB values of $186$. $(186/255)^{2.2} \approx 0.5$, which means that a halftone pattern ...


1

This is a hard problem since the systems do not in fact tell you how it should operate. The problem is that there are several ways to address this issue: Apply a LUT to all output Let the system color manage Let each application color manage Nearly all of our color management systems are borderline braindead. There is really no sane way to ensure that you ...


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