I'm trying to create a simplified hue/saturation picker for cocos2d. I want to create a gradient and to pick from it. I need to recolor a black/white image gradient for every color like blue, red and others. So I need to create many gradients. I know that I should use some blend functions to achieve this.
But I'm still a little bit confused about what is the best way to proceed.
Should I use blend functions at all ?
My problem basically is that I use a gradient from black to transparent or to white but with
sprite.setColor(color);
I get a gradient from black to the desired color but I need a gradient from the desired darker color to white.
What you need to do is create a 2D gradient that goes from unsaturated to saturated left-to-right, and from dark to light bottom-to-top. I'd do it by creating a new bitmap (or if you're using OpenGL, a texture). I'd then color each pixel using the following pseudocode:
hue = <whatever the user set the hue to>
for (row = 0; row < height; row++)
{
for (col = 0; col < width; col++)
{
sat = col / width;
val = row / height;
rgb = HSVToRGB(hue, sat, value);
setPixel (col, row, rgb);
}
}
Related
I am writing a spatial shader in godot to pixelate an object.
Previously, I tried to write outside of an object, however that is only possible in CanvasItem shaders, and now I am going back to 3D shaders due rendering annoyances (I am unable to selectively hide items without using the culling mask, which being limited to 20 layers is not an extensible solution.)
My naive approach:
Define a pixel "cell" resolution (ie. 3x3 real pixels)
For each fragment:
If the entire "cell" of real pixels is within the models draw bounds, color the current pixel as per the lower-left (where the pixel that has coordinates that are the multiple of the cell resolution).
If any pixel of the current "cell" is out of the draw bounds, set alpha to 1 to erase the entire cell.
psuedo-code for people asking for code of the likely non-existant functionality that I am seeking:
int cell_size = 3;
fragment {
// check within a cell to see if all pixels are part of the object being drawn to
for (int y = 0; y < cell_size; y++) {
for (int x = 0; x < cell_size; x++) {
int erase_pixel = 0;
if ( uv_in_model(vec2(FRAGCOORD.x - (FRAGCOORD.x % x), FRAGCOORD.y - (FRAGCOORD.y % y))) == false) {
int erase_pixel = 1;
}
}
}
albedo.a = erase_pixel
}
tl;dr, is it possible to know if any given point will be called by the fragment function?
On your object's material there should be a property called Next Pass. Add a new Spatial Material in this section, open up flags and check transparent and unshaded, and then right-click it to bring up the option to convert it to a Shader Material.
Now, open up the new Shader Material's Shader. The last process should have created a Shader formatted with a fragment() function containing the line vec4 albedo_tex = texture(texture_albedo, base_uv);
In this line, you can replace "texture_albedo" with "SCREEN_TEXTURE" and "base_uv" with "SCREEN_UV". This should make the new shader look like nothing has changed, because the next pass material is just sampling the screen from the last pass.
Above that, make a variable called something along the lines of "pixelated" and set it to the following expression:
vec2 pixelated = floor(SCREEN_UV * scale) / scale; where scale is a float or vec2 containing the pixel size. Finally replace SCREEN_UV in the albedo_tex definition with pixelated.
After this, you can have a float depth which samples DEPTH_TEXTURE with pixelated like this:
float depth = texture(DEPTH_TEXTURE, pixelated).r;
This depth value will be very large for pixels that are just trying to render the background onto your object. So, add a conditional statement:
if (depth > 100000.0f) { ALPHA = 0.0f; }
As long as the flags on this new next pass shader were set correctly (transparent and unshaded) you should have a quick-and-dirty pixelator. I say this because it has some minor artifacts around the edges, but you can make scale a uniform variable and set it from the editor and scripts, so I think it works nicely.
"Testing if a pixel is modifiable" in your case means testing if the object should be rendering it at all with that depth conditional.
Here's the full shader with my modifications from the comments
// NOTE: Shader automatically converted from Godot Engine 3.4.stable's SpatialMaterial.
shader_type spatial;
render_mode blend_mix,depth_draw_opaque,cull_back,unshaded;
//the size of pixelated blocks on the screen relative to pixels
uniform int scale;
void vertex() {
}
//vec2 representation of one used for calculation
const vec2 one = vec2(1.0f, 1.0f);
void fragment() {
//scale SCREEN_UV up to the size of the viewport over the pixelation scale
//assure scale is a multiple of 2 to avoid artefacts
vec2 pixel_scale = VIEWPORT_SIZE / float(scale * 2);
vec2 pixelated = SCREEN_UV * pixel_scale;
//truncate the decimal place from the pixelated uvs and then shift them over by half a pixel
pixelated = pixelated - mod(pixelated, one) + one / 2.0f;
//scale the pixelated uvs back down to the screen
pixelated /= pixel_scale;
vec4 albedo_tex = texture(SCREEN_TEXTURE,pixelated);
ALBEDO = albedo_tex.rgb;
ALPHA = 1.0f;
float depth = texture(DEPTH_TEXTURE, pixelated).r;
if (depth > 10000.0f)
{
ALPHA = 0.0f;
}
}
I want to create a colour scroller effect. I have a function that I give it RGB values (eg. setColor(189,234,45)) and I want to change the colour rapidly but I don't want to get many repeats to create an effect of scrolling through the colours.
I have tried tried the following but it doesn't quite generate the effect that I am looking for.
for (int i = 0; i < 256; i++) {
for (int j = 0; j < 256; j++) {
for (int k = 0; k < 256; k++) {
setColor(i, j, k);
}
}
}
I wanted to know if anyone knows how the colour scroller's colours are arranged next to each other. The arrangement I am looking for looks like the scroll on the right.
The colors you are working with are represented as R,G,B (red green blue) values. However, another
way to think about color is hue, saturation, value. In the scroll image you are trying to emulate,
it is the hue that is changing - the saturation and value (brightness) are unaffected.
Here is a function that happens to make a hue-cycle gradient like the one in the image you linked to:
int n = 256; // number of steps
float TWO_PI = 3.14159*2;
for (int i = 0; i < n; ++i) {
int red = 128 + sin(i*TWO_PI/n + 0) + 127;
int grn = 128 + sin(i*TWO_PI/n + TWO_PI/3) + 127;
int blu = 128 + sin(i*TWO_PI/n + 2*TWO_PI/3) + 127;
setColor(red, grn, blu);
}
To understand how that function works, I recommend that you read my color tutorial that GreenAsJade linked to.
However, that kind of gradient function isn't quite what you need, because you want to start from a particular color you are passing in, and then go to the next color in the sequence. It's much easier to do this kind of thing if you represent your colors as HSV triplets (or HSB triplets), instead of RGB triplets. Then you can manipulate just the hue component, and get those kind of rainbow effects. In helps to have a set of function that can convert from RGB to HSV and back again.
This site contains a bunch of color conversion source code, including the ones you need for those conversions. Using the two conversion functions supplied on that page, your code might look like:
void cycleMyColor(int *r, int *g, int *b) {
float h,s,v, fr,fg,fb;
RGBtoHSV(*r/255.0,*g/255.0,*b/255.0,&h,&s,&v);
h += 1/256.0; // increment the hue here
h -= (int) h; // and cycle around if necessary
HSVtoRGB(&fr,&fg,&fb,h,s,v);
*r = fr*255; *g = fg*255; *b = fb*255;
setColor(*r,*g,*b);
}
This code is a little more complicated than it needs to be because the color conversions on that site use floating point color components that go from 0-1, instead of integers that go from 0-255, as you were using, so I'm spending a few lines converting between those two representations. You may find it simpler to just keep your color in HSB space, and then convert to RGB when you want to display it.
As you mentioned in your edit, you don't like the sequence of colours, because you start from black an end at white, instead of starting at one end of the rainbow and going to the other.
So you are going to need to work out a sequence of RGB that goes from blue through green and yellow to red. That means you need to start with (0,0,255) and end at (255, 0, 0), and don't pass through (255,255,255) or (0,0,0) - in a nutshell, that's how its done.
There are many ways you could do this and get a pleasing effect - beyond the scope of an answer here. This article explores it in depth:
http://krazydad.com/tutorials/makecolors.php
I am working on a shader for Unity in which I want to change the color based on an mask image. In this mask image the RGB channels stand for a color that can be choosen in the shader. The idea behind the shader is that it is easy to change the look of an object without having to change the texture by hand.
Shader "Custom/MultiColor" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_MaskTex ("Mask area (RGB)", 2D) = "black" {}
_ColorR ("Red Color", Color) = (1,1,1,1)
_ColorG ("Green Color", Color) = (1,1,1,1)
_ColorB ("Blue Color", Color) = (1,1,1,1)
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 200
CGPROGRAM
#pragma surface surf Lambert
sampler2D _MainTex;
sampler2D _MaskTex;
half4 _ColorR;
half4 _ColorG;
half4 _ColorB;
half4 _MaskMult;
struct Input {
float2 uv_MainTex;
};
void surf (Input IN, inout SurfaceOutput o) {
half4 main = tex2D (_MainTex, IN.uv_MainTex);
half4 mask = tex2D (_MaskTex, IN.uv_MainTex);
half3 cr = main.rgb * _ColorR;
half3 cg = main.rgb * _ColorG;
half3 cb = main.rgb * _ColorB;
half r = mask.r;
half g = mask.g;
half b = mask.b;
half minv = min(r + g + b, 1);
half3 cf = lerp(lerp(cr, cg, g*(r+g)), cb, b*(r+g+b));
half3 c = lerp(main.rgb, cf, minv);
o.Albedo = c.rgb;
o.Alpha = main.a;
}
ENDCG
}
FallBack "Diffuse"
}
The problem with the shader is the blending between the masked color based on the green and blue channel. Between colors defined in the color supposted to be from the red region is visible. Below a sample is visable.
The red color is create by the red mask, green by the green mask and desert yellow by the blue region. I do not know why this happens or how to solve this problem.
Best guess: anti-aliasing or image compression. Aliasing (on the brush your using) will cause an overlap in the color channels, causing them to mix. Compression usually works by averaging each pixel's color info based on the colors around it (jpeg is especially notorious for this).
Troubleshoot by using a straight pixel based brush (no aliasing, no rounded edges) in Photoshop (or whatever image suite you're using) and/or try changing the colors through your shader and see how they mix- doing either should give you a better idea of what's going on under the hood. This combined with an lossless/uncompressed image-type, such as .tga should help, though they may use more memory.
Is there any way to fill an ellipse or a rect by point to point like in an airbrush tool in mspaint?
I could not find a way to create an empty rect or an ellipse and then fill them up pixel by pixel or setting random pixels on screen in a circle way....
Can i tell setPixel to fill inside a dcellipse or anything like that?
10x
You need to create a region with CRgn, then select that as the clipping region in your CDC with SelectClipRgn. Then you can use CDC::SetPixel to set random pixels anywhere within the bounding rectangle of your shape, and only the ones within the clipping region will be painted.
Be aware that this will be slow, and will need to be redone every time the window paints (such as when another window is dragged over it).
In your "make random pixels" loop, just exclude the pixel if it's outside your desired circle.
num_pixels = 20; // how many pixels
circle_radius = 32; // 32-pixel radius, or whatever you'd like
circle_radius2 = circle_radius * circle_radius;
while (num_pixels-- > 0)
{
// get a random number between (-circle_radius / 2, circle_radius / 2)
pixel_x = rand(circle_radius) - circle_radius / 2;
pixel_y = rand(circle_radius) - circle_radius / 2;
// compute squared distance between generated pixel and radius,
// exclude if out of range
if ( (center_x - pixel_x) * (center_x - pixel_x) +
(center_y - pixel_y) * (center_y - pixel_y) > circle_radius2 )
continue; // generate another pixel
// do stuff with pixel
}
Given two colors and n steps, how can one calculate n colors including the two given colors that create a fade effect?
If possible pseudo-code is preferred but this will probably be implemented in Java.
Thanks!
Divide each colour into its RGB components and then calculate the individual steps required.
oldRed = 120;
newRed = 200;
steps = 10;
redStepAmount = (newRed - oldRed) / steps;
currentRed = oldRed;
for (i = 0; i < steps; i++) {
currentRed += redStepAmount;
}
Obviously extend that for green and blue.
There are two good related questions you should also review:
Generating gradients programatically?
Conditional formatting — percentage to color conversion
Please note that you're often better off doing this in the HSV color space rather than RGB - it generates more pleasing colors to the human eye (lower chance of clashing or negative optical properties).
Good luck!
-Adam
If you want a blend that looks anything like most color picker GUI widgets, you really want to translate to HSL or HSV. From there, you're probably fine with linear interpolation in each dimension.
Trying to do any interpolations directly in RGB colorspace is a bad idea. It's way too nonlinear (and no, gamma correction won't help in this case).
For those looking for something they can copy and paste. Made a quick function for RGB colors. Returns a single color that is the amount of ratio closer to rgbColor2.
function fadeToColor(rgbColor1, rgbColor2, ratio) {
var color1 = rgbColor1.substring(4, rgbColor1.length - 1).split(','),
color2 = rgbColor2.substring(4, rgbColor2.length - 1).split(','),
difference,
newColor = [];
for (var i = 0; i < color1.length; i++) {
difference = color2[i] - color1[i];
newColor.push(Math.floor(parseInt(color1[i], 10) + difference * ratio));
}
return 'rgb(' + newColor + ')';
}
The quesiton is what transformation do you want to occur? If you transpose into the HSV colourspace and given
FF0000 and 00FF00
It will transition from red through yellow to green.
However, if you define "black" or some other shade as being the mid-point of the blend, you have to shade to that colour first ff0000->000000->00ff00 or via white : ff0000 -> ffffff -> 00ff00.
Transforming via HSV however can be fun because you have to use a bit of trig to map the circular map into the vector components.
The easiest thing to do is linear interpolation between the color components (see nickf's response). Just be aware that the eye is highly nonlinear, so it won't necessarily look you're making even steps. Some color spaces attempt to address this (CIE maybe?), so you might want to transform into another color space first, interpolate, then transform back to RGB or whatever you're using.
How about this answer
- (UIColor *)colorFromColor:(UIColor *)fromColor toColor:(UIColor *)toColor percent:(float)percent
{
float dec = percent / 100.f;
CGFloat fRed, fBlue, fGreen, fAlpha;
CGFloat tRed, tBlue, tGreen, tAlpha;
CGFloat red, green, blue, alpha;
if(CGColorGetNumberOfComponents(fromColor.CGColor) == 2) {
[fromColor getWhite:&fRed alpha:&fAlpha];
fGreen = fRed;
fBlue = fRed;
}
else {
[fromColor getRed:&fRed green:&fGreen blue:&fBlue alpha:&fAlpha];
}
if(CGColorGetNumberOfComponents(toColor.CGColor) == 2) {
[toColor getWhite:&tRed alpha:&tAlpha];
tGreen = tRed;
tBlue = tRed;
}
else {
[toColor getRed:&tRed green:&tGreen blue:&tBlue alpha:&tAlpha];
}
red = (dec * (tRed - fRed)) + fRed;
green = (dec * (tGreen - fGreen)) + fGreen;
blue = (dec * (tBlue - fBlue)) + fBlue;
alpha = (dec * (tAlpha - fAlpha)) + fAlpha;
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}