Questions tagged [color]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1
vote
0answers
29 views

Weird glColor3f results in framebuffer objects

The code is glColor3f(1, 1, 1); gluSphere(gluq, 0.2, 10, 10); glColor3f(1, 0, 0); glTranslatef(1, 0, 0); gluSphere(gluq, 0.2, 10, 10); In short, when I draw ...
1
vote
0answers
38 views

Reddish tint with spectral renderer

I'm trying to implement a spectral path tracer and comparing results from my program with renders of the same scene done with pbrt and ...
0
votes
0answers
27 views

Custom background color

I am exporting an OpenSCAD file with OpenSCAD with: openscad model.scad -o model.png --imgsize=1920,1080 --camera 400,300,150,74,0,0,8000 I can set the image ...
7
votes
2answers
219 views

Why is the CMYK space four sided in chromaticity charts

In chromaticity charts the CMYK color space is usually four-sided. I've lately had to read quite a few charts and it suddenly dawned to me that I don't really understand why. It has just not been ...
0
votes
0answers
91 views

Sub pixel rendered white text on black background changes color when resized to a very small size

download: https://upload.wikimedia.org/wikipedia/commons/5/57/Subpixel-rendering-RGB.png The above picture is an example for sub pixel rendering. I tried resizing the image to very small size in ...
1
vote
2answers
280 views

How are colors really mixed?

I'm kind of stuck on this one. When following a conventional, high-level shading tutorial, you'll come across these images that are like ambient + diffuse + specular = result, but I can tell that it's ...
1
vote
1answer
68 views

Some questions about working in 0-255 integers instead of single precision floating point colors

I have many objects that store their color values. At the moment I'm storing them as vec4 values, that is four 4-byte values for RGBA, mainly because this is how the shader reads them. I was thinking ...
3
votes
1answer
79 views

Tiled Image Palettization Algorithm?

In most cases today, image palettization consists of reducing the overall number of colors in an image to some fixed number globally. This is typically solved as a straightforward but computationally ...
0
votes
0answers
89 views

Path tracing - Better images without Gamma correction?

So I read about tonemapping and Gamma Correction recently and have implemented it in my path tracer. For the time being I'm using Reinhard tonemapping operator as described in his paper $L_d = L_w *...
4
votes
1answer
62 views

Getting contrast color to a given color in RGB or ARGB or HEX

I am looking for a stable way to find a contrast/inverted/opposite color to a given one. Application of this is to find best possible color for foreground to give background.
2
votes
1answer
87 views

Computing sRGB color from SPDs

I'm trying to write my own spectral path tracer and a bit stuck with converting computed SPDs to LDR RGB values. What I'm doing right now is convert sampled SPDs (in ...
4
votes
1answer
71 views

How to shift color values of a single RGB channel

I’m a weaver and textile maker with no prior coding or programming experience. In researching and reading through posts on this and other message boards, I was able to find a lot of useful information,...
2
votes
2answers
261 views

How can I draw this style of grid?

I'm trying to write code (in any language) to render this 3D grid, matching the look and colors as closely as possible:
1
vote
1answer
26 views

Converting color to equivalent with opacity

Assume a color X with alpha 1 and RGB 255,230,210. How can i find another color with alpha A ( or an array of colors ) that blended with a background of color Y ( e.g 255,255,255 ) would produce the ...
12
votes
4answers
684 views

For shader math, why should linear RGB keep the gamut of sRGB?

sRGB is often contrasted with "linear RGB." Images are stored on disk and passed to displays in sRGB, which is approximately perceptually uniform in intensity. Shader math is done in linear RGB, ...
8
votes
1answer
297 views

How to correctly render visible spectrum with uniform intensity?

I'm trying to get the correct representation of visible spectrum to render on the screen. My current progress is with using CIE 1931 standard observer color matching functions analytically ...
1
vote
1answer
37 views

How to blend a segment of an image with another image

I want to put a segment of an image to another image. But to make it realistic I applied poisson blending. But the output is not good at all. Output without poisson blending. The kid was cropped ...
3
votes
1answer
60 views

Repeating alpha over/under operation multiple times

I have two RGBA colors in linear [0..1] space, src and dst and I want to alpha blender src ...
2
votes
1answer
47 views

Will sRGB color space get replaced by wider gamut [closed]

in future, will sRGB which is a common standard monitor color space nowadays be taken the place by the wider gamut color spaces? since wide gamut monitor keep publishing in the market and may be ...
4
votes
1answer
533 views

How do I calculate average hue, since the numbers loop around?

If I calculate the average (mean) hue of a set of colours naively, I will get silly answers sometimes. For example, in HSB/HSL, the average of hue=10 (slightly orange red) and hue=350 (slightly blue ...
2
votes
2answers
259 views

Calculate the average color of an image

I want to calculate the average color+opacity of an image. First I thought about just averaging all ARGB values component-wise, but this got really dark on images with a lot of transparency. I also ...
16
votes
2answers
458 views

Is gamma still important to take into account?

Do different monitors (including mobile screens) still use significantly different gamma functions when displaying colour images? Is there a standardised way to represent colour that can then be ...
4
votes
1answer
121 views

Can someone explain this formula for parse RGB to HSL?

Im trying to complain the algorithm to calculate the HSL value form a RGB color. I understand the algorithm for the Hue, but im lost with the Lightness and saturation. Someone can explain why? There ...
1
vote
1answer
89 views

Understanding material .mtl files

I am reading this piece of documentation to understand mtl files So far I am stuck trying to understand the difference between ambient, diffuse and specular reflectivity (Ka, Kd, Ks). If I am ...
3
votes
2answers
153 views

Why does _ray_ tracing work?

Perspective projection (or at least non-orthogonal) is by far the most common in photo-realistic graphics. When we use perspective projection, the (equally thick) slices of volume visualized by each ...
1
vote
1answer
43 views

Determine paint color from a photo

I ran into this problem while trying to find the paint color of the doors in my house: is it in principe possible to automatically determine the paint color from a photo? Different types of colour ...
2
votes
1answer
262 views

YUV to HSV to RGB issues

As per this resource, there is an easy way to convert from YCbCr to HSV. Saturation is sqrt(Cb^2 + Cr^2). Now here is my issue. If I take pure red (1,0,0), green(0,1,0), and blue(0,0,1) colors, ...
5
votes
2answers
260 views

Calculate an equally bright grey to a linear RGB colour

I'm trying to get a grey linear-RGB-triple that is equally bright as another (colorful) RGB-triple. I have to admit, that there is great confusion for me with all the color stuff, even though I read ...
3
votes
1answer
122 views

How can I implement GIMP's “Colorize” function?

I have an RGB pixel that I'd like to colorize in my program (I'm using GLSL) very similar to how the GIMP "Colors > Colorize" function works. In my program, I can easily convert between RGB and HSV. ...
1
vote
2answers
456 views

Change particular color in an image

Suppose i have a image and I want to convert the portion of image that is red to blue(or any other color). One way to do this is extract red part of image using HSV or other color values and convert ...
1
vote
1answer
84 views

Quick 2-color quantization for small images

So I have a small (8x8 pixel) image in 24-bit color. I want to be able to (quickly) generate a color-quantized version of the image that only has two colors. One naive approach is to cluster a luma ...
1
vote
1answer
46 views

What remedies are there for percieved color artifacts due to pixel geometry?

I have a white line on black background. Because of the pixel geometry the line does not look really white; one edge looks red-isch, the other blue-isch. Other fore- and background yield other ...
12
votes
2answers
1k views

What would be the correct way to calculate saturation in this case?

I'm trying to make a HSV representation of the xyY color space. To calculate hue from an $(x, y)$ color, I use the angle between that color and red (wavelength 745) on the xy chromacity diagram, with ...
1
vote
2answers
110 views

Can I get numeric data from a color map?

In my class I often need to work with color map images. I would show the image and try to make inferences/observations about different subjects. Often times I need to actually quantify some aspects, ...
4
votes
1answer
98 views

Generating and Combining Spectral Colors

I have two somewhat related questions to ask: What is the most accurate way to get the colors of a spectrum, without having to go deep into physics and simulating the universe? ;) Right now, I'm ...
4
votes
1answer
140 views

How do you deal with clipping when rendering to a limited colorspace?

In my naïve raytracer experiment I work internally with RGB values, and after all the tracing has been done, I end up with raw RGB triplets that I need to write down to some image format with a ...
3
votes
0answers
141 views

Color of the Sky [closed]

What is the color of the sky depending on the time? I'm looking for a set of colors (HTML-Code), the sky has during sunrise, morning, forenoon, noon, afternoon, evening and sunset. A formula to ...
1
vote
1answer
688 views

RGB nonlinear, what does it mean?

What does it mean and why is it not well suited for describing colors by human? Is CMYK nonlinear also?
6
votes
1answer
120 views

What determines the color gamut of a display?

I’m not sure if I’m posting this question in the right area but, I’m wondering what determines the color gamut of a display? Is or hardware down to the RGB filter built into a display like a monitor ...
6
votes
2answers
341 views

Color transform algorithm (that also works on saturation and value/lightness)?

To change particular colors in an image, generally you multiply the RGB by a transformation matrix. Image manipulation programs such as gimp & photoshop have a selective color change function that ...
1
vote
1answer
64 views

Extracting the green-screen region borders

Given a png image with an unknown number of green colored (rgba=0, 65535, 0, 65535) regions 1- How can I find and put the border points of only the separate green boxes to an array like: ...
17
votes
5answers
5k views

Why do red, green, and blue make up all the colors?

Why do red, green, and blue combinations can make up all the visible colors?
4
votes
0answers
92 views

How to properly color particles in N body sim?

In my n-body simulation I would like to color the particles in way which corresponds to the magnitude of the net force acting on them. This is so that I can confirm visually that the particles ...
1
vote
0answers
77 views

What causes this color shift?

Below are the original image and a JPEG encoded/decoded image. To my untrained eyes, cyan becomes yellow, yellow becomes magenta, and magenta becomes cyan. Obviously there's a problem with the ...
4
votes
2answers
262 views

Suggested image preprocessing before applying threshold

I am trying to vectorize the contours (skewed rectangle) of the TV in the following original image. My first step is applying threshold. Tried selection of threshold values based on what skimage has ...
1
vote
1answer
248 views

correct rgb or cmyk code from some proportion of cyan, magenta and yellow

I am trying to find a way to go from some proportion of cyan, magenta and yellow where: cyan: 33 % + magenta : 33% + yellow : 33% = 100% black so each is represented as a percentage of the sum ...
1
vote
0answers
85 views

Why does this edge detect show different results for the same color combinations?

I'm researching highlighting accessible color contrast via filter operations. I have a test screenshot of SRGB hex values compared with WCAG's official contrast algorithm: I converted it to its ...
3
votes
1answer
140 views

What is the name of the RGB thing I want to be able to do, and what free program(s) can do it automatically?

I'm gonna start this off with an... "indexed image"? If that's the proper term for it? If this 384x144 image were actually only the top-left 192x48 pixels (I'll refer to that portion as "0,0"), I ...
4
votes
2answers
327 views

What are the advantages of having two chroma channels and a luma channel vs. three chroma channels?

RGB has the advantage over schemes like YPBPR in that it's more intuitive to understand, so why use the latter? The only advantage I can think of right now is that it allows you to encode greyscale ...
8
votes
2answers
1k views

What is a good color similarity metric?

I have some colors in RGB in [0,1] and want to find a way to rate their similarity, as perceived by a human. I have two ideas in mind, but I am sure there are other options as well, but am unsure ...