I have a UISlider that is supposed to update the color of a textlabel. Now I want the user to be able to choose between all colors in the spectrum (sort of all anyway). I was thinking of using this UISlider to represent the colors and when dragging the slider the value/color changes.
I know the spectrum is not sequential like: [0,0,0]...[255,0,0]...[255,1,0]...[255,255,0] etc.
So: any tip on how I can implement this?
Color is at least a two or three dimensional selection. And a slider only provides a scalar output. If you want a smoothly changing selection using only a scalar parameter, you might try drawing a path line on some color chart (or a functional representation thereof) and select a point on that path parametrically.
Yes, color is a multidimensional value, but there are different ways to slice those dimensions. I think a hue, saturation, brightness constructor, rather than RGB, will give you exactly the effect you want. For example, often I will generate a random color with [UIColor colorWithHue:<random float in [0,1]> saturation:1.f brightness:1.f alpha:1.f].
Slide hue linearly from 0 to 1, with saturation and brightness fixed at the most legible (or whatever) values.
Related
So I'm trying to create a gradient fill for a line chart. The thing about this gradient is that I need it to have a color according to a given value.
So, what I was thinking is that if I could change the orientation of the gradient (from side to side instead of down-up) I could give it a color scheme based on the values. However, I haven't been able to "transpose" the gradient.
My expected result is something like this:
Another value (a 3rd one), which is not the line value (Y-axis), or the date (X-axis) gives the color for the gradient at any X-axis point
Any ideas?
Thanks!
I have a Packed Bubble dashboard. My Y axis is a list of names and my X axis is a decimal. I want each differing number to be a different color. Can I do this manually?
If you want to color each bubble with a separate color just use the field that each bubble represent in the color shelf. If I understood your data correctly, each bubble basically represents one campaign, so you should use that as the color.
You can manually assign color using Color>Edit Color and assigning the color of your choice.
See image 1.
If you want to color your bubbles based on your measure AVg(NPV/Marketing $) you can do as Alex Blakemore mentioned and use your measure as a stepped color or gradient.
You can use Color>Edit Color here too , in this case manually assigning color is a bit difficult. But if you play with number of steps, the gradient pre-select, etc, you can usually get very close to what ever your wanted it to look like.
Put your numeric field on the color shelf, and either edit the colors to use a stepped set of colors - or change the field to be discrete and choose individual colors to taste.
I need to implement an image segmentation function in MATLAB based on the principles of the connected components algorithm, but with a few modifications. This is intended for very simple, 2D images, with a background color and some objects in different colors.
The idea is that, taking the image as a matrix, I provide a tool to select the background color (it will vary for every image). Then, when the value of the color of the background of the image is selected, I have to segment all the objects in the image, and the result should be a labeled matrix, of the same size of the image, with 0's for the background, and a different number for each object.
This is a graphic example of what I mean:
I understand the idea of how to do it, but I do not know how to implement it on MATLAB. For each pixel (matrix position) I should mark it as visited and then if the value corresponds to the one of the background, assign 0, if not, assign another value. The objects can be formed by different colors, so in the end, I need to segment groups of adjacent pixels, whatever their color is. Also I have to use 8-connectivity, in order to count the green object of the example image as only one object and not 4 different ones. And also, the objects should be counted from top to bottom, and from left to right.
Is there a simple way of doing this in MATLAB? I know the bwlabel function, but it works for binary images only, so I'd like to adapt it to my case.
once you know the background color, you can easily convert your image into a binary mask of the same size:
bw=img!=bg_color;
Once you have a binary mask you can call bwlavel with 8-connectivity argument as you suggested yourself.
Note: you might want to convert your color image from RGB representation to an indexed image using rgb2ind before processing.
I know how get a random UIColor, but I wonder if exist a way to only return colors with some specific quality of it. I don't know if exist a specific term, but for example, I need to get only opaque colors, dark tones... colors that are good for backgrounds with bright text/ images on it.
I could hand-pick some, but in my case i want to provide a very good defaults for a large list of icons backgrounds.
UPDATE:
My solution based on the answer here:
float r = arc4random() % 12;
return [UIColor colorWithHue:(30*r)/360 saturation:0.5f brightness:0.8f alpha:1.0f];
I get a very small list of possible answers, but this give me a good start.
What I would do is use the HSV/HSL colour space and then convert the results to RGB. Keep a constant value and saturation (S and V) whose qualities you like, and then alter the hue (H) value for the number of colours you want. Convert the results to RGB and you'll have a nice set of colours that appear to work well together. You can create any set of nice colours that are 'saturated', 'bright', 'dark', etc. just by picking nice combinations of S and V for your needs (low V is dark, high V is bright, low S is unsaturated, high S is saturated).
Take a look at this wiki page for a discussion on converting HSV to RGB. I'd recommend you start with saturation (S) at 0.5 and value (V) at 0.8. Then, to generate nice colours, do the HSV -> RGB conversion for H values of 0, 30, 60, 90... all the way up to 360. It will generate a nice palette of colours that look good together. Later, you can adjust your S and V values if you want different colour 'qualities'.
Using a random color as a background is indeed a suboptimal solution as it will lead to visibility and readability problems of the text and information of your icon. There is some research going on in automatically finding an appropriate color that matches your foreground colors, leading to a harmonic result in terms of visual perception of the image. Have a look at http://cs.nyu.edu/~sorkine/ProjectPages/Harmonization/
For image scanning purposes, I'd like a pixel (which I can get from a UIImage) to match (for a certain percentage) to a pre-set color.
Say pink. When I scan the image for pixels that are pink, I want a function to return a percentage of how much the RGB value in the pixel looks like my pre-set RGB value. This way I'd like all (well, most) pink pixels to become 'visible' to me, not just exact matches.
Is anyone familiar with such an approach? How would you do something like this?
Thanks in advance.
UPDATE: thank you all for your answers so far. I accepted the answer from Damien Pollet because it helped me further and I came to the conclusion that calculating the vector difference between two RGB colors does it perfectly for me (at this moment). It might need some tweaking over time but for now I use the following (in objective c):
float difference = pow( pow((red1 - red2), 2) + pow((green1 - green2), 2) + pow((blue1 - blue2), 2), 0.5 );
If this difference is below 85, I accept the color as my target color. Since my algorithm needs no precision, I'm ok with this solution :)
UPDATE 2: on my search for more I found the following URL which might be quite (understatement) useful for you if you are looking for something similar.
http://www.sunsetlakesoftware.com/2010/10/22/gpu-accelerated-video-processing-mac-and-ios
I would say just compute the vector difference to your target color, and check that it's norm is less than some threshold. I suspect some color spaces are better than others at this, maybe HSL or L*ab, since they separate the brightness from the color hue itself, and so might represent a small perceptual difference by a smaller color vector...
Also, see this related question
Scientific answer: You should convert both colors to the LAB color space and calculate the euclidian distance there. That value is also called deltaE.
The LAB space was developed (using test persons) for exactly that reaason: so that different color pairs with equal distances in tnis space correspond to equal perceived color differences.
However, it sounds like you are not looking for matching a specific color, but rather a color range (lets say all skin tones). That might require more user input than just a reference color + a deltaE tollerance:
a reference color with 3 tollerances for hue, saturation and brightness
a cloud of refence color samples
...