Below COLOR/INDEX are information that I want to use for heatmap color palette
COLOR= ['#36abdf','#84d9a3','#f4d646','#e86000','#ff0000','#671b1b']
INDEX= [0, 0.001, 10, 25, 50, 75, 1]
I'm trying to make some HEATMAP which havs continuous (Gradient) color value.
My original Intension was that
Set Blue color ('#36abdf') for only '0' vlaue,
If value is bigger than 0, must start with green color('#84d9a3') and be gradually changed within color set for bigger value.
I found some code that can make LinearColormap through branca.colormap
cmap = b_cm.LinearColormap(colors=['#36abdf','#84d9a3','#f4d646','#e86000','#ff0000','#671b1b'], index=[0,0.001,25,50,75,90],vmin=0,vmax=100)
but it seems that I cannot use LinearColormap for color palette in seaborn/matplotlib heatmap
please let me introduce code that make color palette that I want.
I will be so appreciate if you let me know.
thx!!
Related
(Hello, it's my first ever post here)
here's what I'd like to incorporate in this simple example:
I would like to make the background turn from light to dark gradually when the user is closer to a particular orientation – in this case (example above) the desired orientation is a steep angle so that the foreshortened anamorphic image looks like a regular skull (the value of the background indicating the angle user should aim for – kind of like playing Hot and Cold)
when the user reaches the desired orientation (the background is then accordingly 100% dark) I would like it to lock rotation and trigger a video file in the background or a pop up window.
I assume it has to do with accessing the camera rotation values inside OrbitControls and setting some kind of an Event?? i have no idea how to access it.
Any kind of help, suggestions to edit the thread or explanation would be greatly appreciated, thank you so much in advance!
You could use camera.position to calculate the best vantage point. First, you have to figure out what the desired position is (I'm not sure how the wooden board is being placed, but this position seems to be close to: { x: 6.8, y: 0.6, z: -1.8})
var vantagePoint = new THREE.Vector3(6.8, 0.6, -1.8);
var distance = 100;
var normalized = 1;
var endColor = new THREE.Color(0xff9900);
var startColor = new THREE.Color(0x0099ff);
scene.background = startColor;
animate() {
distance = vantagePoint.distanceTo(camera.position);
normalized = THREE.Math.smoothstep(distance, 5, 100); // Converts [1, 100] => [0, 1]
// Resets the color on each frame
startColor.set(0x0099ff);
startColor.lerp(endColor, normalized);
}
The closer to 0 you are, the closer you are to seeing the skull. You can then use that value to change the color of scene.background. Anything beyond 10 and you're 'cold', and you get hotter as you approach 0.
https://threejs.org/docs/#api/en/math/Vector3.distanceTo
Update:
You can then transform the distance to a normalized value in the range of [0, 1] by using Math.smoothstep(). Then interpolate the value of the colors with this normalized value using Color.lerp
Repeatedly drawing a semi-opaque black rectangle over the entire canvas before each animation frame is an easy way to get an afterimage effect for moving shapes and it gives me exactly what I need - up to a point. With too slow a fade it doesn't fade all the way to black. Here's an example:
var canv = document.createElement('canvas');
document.body.appendChild(canv);
var ctx = canv.getContext('2d');
ctx.fillStyle = 'rgba(0, 0, 0, 1)';
ctx.fillRect(0, 0, 100, 100);
ctx.fillStyle = 'rgba(255, 255, 255, 1)';
ctx.fillRect(20, 20, 60, 60);
window.requestAnimationFrame(doFade);
function doFade() {
// Never fades away completely
ctx.fillStyle = 'rgba(0, 0, 0, 0.02)';
ctx.fillRect(20, 20, 60, 60);
window.requestAnimationFrame(doFade);
}
jsfiddle
This looks to me like a numeric precision problem - you can't expect the canvas to keep floating point pixel values around - but I'm not sure how to get around this.
I tried reading the image into a pattern, blanking the canvas, and then filling with the pattern at lower opacity in the hope that I could make rounding error work in my favor, but it seems to have the same result.
Short of reading out the image data and setting to black any pixels below a certain threshold, which would be prohibitively slow, I'm running out of ideas and could use some suggestions.
Thanks!
I thought I'd share my solution for the benefit of anyone else who might run into this problem. I was hoping to avoid doing any pixel-level manipulation, but beyond a certain threshold it's just not possible with the built-in canvas operations because the underlying bitmap is only 8 bits per channel and small fades will work out to less than one least significant bit and won't have any effect on the image data.
My solution was to create an array representing the age of each pixel. After each frame is drawn, I scan the imageData array, looking only at the alpha channel. If the alpha is 255 I know the pixel has just been written, so I set the age to 0 and set the alpha to 254. For any other non-zero alpha values, I increment the pixel age and then set the new alpha based on the pixel age.
The mapping of pixel age to alpha value is done with a lookup table that's populated when the fade rate is set. This lets me use whatever decay curve I want without extra math during the rendering loop.
The CPU utilization is a bit higher, but it's not too much of a performance hit and it can do smooth fades over several seconds and always fades entirely to black eventually.
Explanation
I have a semi-transparent color of unknown value.
I have a sample of this unknown color composited over a black background and another sample over a white background.
How do I find the RGBA value of the unknown color?
Example
Note: RGB values of composites are calculated using formulas from the Wikipedia article on alpha compositing
Composite over black:
rgb(103.5, 32.5, 169.5)
Composite over white:
rgb(167.25, 96, 233.25)
Calculated value of unknown color will be:
rgba(138, 43, 226, 0.75)
What I've Read
Manually alpha blending an RGBA pixel with an RGB pixel
Calculate source RGBA value from overlay
It took some experimentation, but I think I figured it out.
Subtracting any of the color component values between the black and white composite should give you the inverse of the original color's alpha value, eg:
A_original = 1 - ((R_white_composite - R_black_composite) / 255) // in %, 0.0 to 1.0
It should yield the same value whether you use the R, G, or B component. Now that you have the original alpha, finding the new components is as easy as:
R_original = R_black_composite / A_original
G_original = G_black_composite / A_original
B_original = B_black_composite / A_original
I'm not really getting the glBlendFunc() function and how it works.
Is there a blend mode that lets destination black be black while overriding any other dst colour?
I have a black and white canvas containing colouring edges and shapes. I'd like to draw a brush anywhere over the canvas but not overriding the edges so they remain black once the image is fully coloured. Ideally, since the destination has some grey around the edges for smoothness, the grey shades would be tinted with the brush colour.
Thank you!
I believe what you need is glBlendFunc(GL_DST_COLOR, GL_ZERO).
To explain you how the blend function works:
When blending you have 2 colours, source and destination. Source is the colour you are trying to apply (a textel, a solid colour...). Destination is the colour currently on the buffer. The 2 parameters in the glBlendFunc tell how to multiply the source and destination colour before adding them together to get the result colour.
So in the case of glBlendFunc(GL_DST_COLOR, GL_ZERO) and having a black and white destination buffer (as you described) will act like this:
if destination colour is white (1,1,1,1) and you will apply some colour for instance (.1, .2, .3, 1) the result will be R = (.1, .2, .3, 1)*(1,1,1,1) + (1,1,1,1)*(0,0,0,0) = (.1, .2, .3, 1)
if destination colour is black (0,0,0,0) and you will apply some colour for instance (.1, .2, .3, 1) the result will be R = (.1, .2, .3, 1)*(0,0,0,0) + (0,0,0,0)*(0,0,0,0) = (0, 0, 0, 0)
if destination colour is grey (.5,.5,.5,1.0) and you will apply some colour for instance (.1, .2, .3, 1) the result will be R = (.1, .2, .3, 1)*(.5,.5,.5,1.0) + (.5,.5,.5,1.0)*(0,0,0,0) = (.05, .1, .15, 1)
This case of yours is a bit specific but in most cases the alpha channel is only used. For instance most common blending is glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) which means the source colour will be multiplied with source alpha while the destination colour will be multiplied with 1.0-source alpha, so a white shape with alpha of .75 over a grey background RGB .5 (any alpha) will result in RGB all 1.0*.75 + .5*(1.0-.75) = .75 + .125 = .875.
Note that this procedure of yours might cost you if you will need some other blending type on the overlay. In that case you will need to look into stencil buffers. Another issue is you might not want to see the black and white part on places you do not draw the overlay. In this case you can simply use the destination alpha to do this blending for you: glColorMask can help you draw only to the alpha channel of your buffer where you can use alpha .0 for "black" areas and 1.0 for "white" areas, when drawing a shape over the buffer you would then use glBlendFunc(GL_DST_ALPHA, GL_ZERO).
If I have matrix/data with line intensity values:
e.g.
0, 1, 2, 3, 4, 5, ..... M (where intensity value is gradually changing)
or
any random order of values
So if I use the first intensity set of data, (0, 1, 2, 3, 4, 5, ..... M), my line color should be gradually turning black to white. If I remember correctly, 0 is used to represent black and 255 is used to represent white? I would like to use a data of intensity values to draw 3D line with changing color/intensity.
How can I draw a 3D line with changing intensity/grayscale? I would appreciate any advice or recommendation.
You can use the 3D colored line plot tool from the file exchange and change the colormap to whatever you need.