We Keep Coding

Calculate middle color beetwen startColor and EndColor

Need to get middle color beetwen startColor and endColor.
If startColor is "red", endColor is "green", then need to get yellow.
If startColor is "red", endColor is "yellow", then need to get orange and so on.
i've started from default red(start) and green(end) colors.
i have found some formula, in most cases return right color but not always, so need to calculte right percent step.
As you can see from image additional colors yellow(start) and green(end) makes one more green...
public static string LerpHue(Color min, Color max)
{
float t = 0.7F // **percent step, need to calculate somehow...**
float minHue = min.GetHue() / 255;
float maxHue = max.GetHue() / 255;
float scale = maxHue - minHue;
float curHue = minHue + (scale * t);
double r, g, b;
HSVToRGB(curHue, 1.0, 1.0, out r, out g, out b);
Color color = Color.FromArgb((int)(r * 255), (int)(g * 255), (int)(b * 255));
return $"#{color.R.ToString("X").PadLeft(2, '0')}{color.G.ToString("X").PadLeft(2, '0')}{color.B.ToString("X").PadLeft(2, '0')}";
}
public static void HSVToRGB(double H, double S, double V, out double R, out double G, out double B)
{
if (H == 1.0)
H = 0.0;
double step = 1.0 / 6.0;
double vh = H / step;
int i = (int)System.Math.Floor(vh);
double f = vh - i;
double p = V * (1.0 - S);
double q = V * (1.0 - (S * f));
double t = V * (1.0 - (S * (1.0 - f)));
switch (i)
{
case 1: { R = q; G = V; B = p; break; }
case 2: { R = p; G = V; B = t; break; }
case 3: { R = p; G = q; B = V; break; }
case 4: { R = t; G = p; B = V; break; }
case 5: { R = V; G = p; B = q; break; }
default:{ R = V; G = t; B = p; break; }
}
}
Help please)

protected void GetCalculatedColor()
{
var colorRangesCount = MeasureAppearance.GaugeRanges.Count;
int step = 1;
var startRange = MeasureAppearance.GaugeRanges.FirstOrDefault();
var endRange = MeasureAppearance.GaugeRanges.LastOrDefault();
Color startColor = Color.FromArgb(int.Parse(startRange?.Color.Replace("#", "") ?? "0", System.Globalization.NumberStyles.AllowHexSpecifier));
Color endColor = Color.FromArgb(int.Parse(endRange?.Color.Replace("#", "") ?? "0", System.Globalization.NumberStyles.AllowHexSpecifier));
foreach (var gaugeRange in MeasureAppearance.GaugeRanges)
{
if (gaugeRange == startRange || gaugeRange == endRange)
continue;
var calculatedColor = ColorService.LerpHueReal(startColor, endColor, (1f / (colorRangesCount - 1)) * step);
gaugeRange.Color = calculatedColor;
step++;
}
}
public static string LerpHueReal(Color start, Color end, float t)
{
var startHue = start.GetHue();
var endHue = end.GetHue();
var interpolatedHue = Math.Min(Math.Max((startHue + (endHue - startHue) * t), 0f), 360f);
var rgb = ColorService.ColorFromHSV(interpolatedHue, 1f, 1f);
return $"#{rgb.R:X2}{rgb.G:X2}{rgb.B:X2}";
}
private static Color ColorFromHSV(float hue, float saturation, float value)
{
int hi = Convert.ToInt32(Math.Floor(hue / 60)) % 6;
double f = hue / 60 - Math.Floor(hue / 60);
value = value * 255;
int v = Convert.ToInt32(value);
int p = Convert.ToInt32(value * (1 - saturation));
int q = Convert.ToInt32(value * (1 - f * saturation));
int t = Convert.ToInt32(value * (1 - (1 - f) * saturation));
if (hi == 0)
return Color.FromArgb(255, v, t, p);
else if (hi == 1)
return Color.FromArgb(255, q, v, p);
else if (hi == 2)
return Color.FromArgb(255, p, v, t);
else if (hi == 3)
return Color.FromArgb(255, p, q, v);
else if (hi == 4)
return Color.FromArgb(255, t, p, v);
else
return Color.FromArgb(255, v, p, q);
}

C# setHue (or alternatively, convert HSL to RGB and set RGB)

C# has a very convenient getHue method, but I can't find a setHue method. Is there one?
If not, I think the best way to define a color after changing the hue would be to convert the HSL value to RGB, and then set the RGB value. I know there are formulas on the internet for doing this, but how would I best go about performing this conversion from HSL to RGB using C#?
Thank You

To set the Hue you create a new Color, maybe from a given one by using GetHue and GetSaturation. See below for the getBrightness function!
I'm using this:
Color SetHue(Color oldColor)
{
var temp = new HSV();
temp.h = oldColor.GetHue();
temp.s = oldColor.GetSaturation();
temp.v = getBrightness(oldColor);
return ColorFromHSL(temp);
}
// A common triple float struct for both HSL & HSV
// Actually this should be immutable and have a nice constructor!!
public struct HSV { public float h; public float s; public float v;}
// the Color Converter
static public Color ColorFromHSL(HSV hsl)
{
if (hsl.s == 0)
{ int L = (int)hsl.v; return Color.FromArgb(255, L, L, L); }
double min, max, h;
h = hsl.h / 360d;
max = hsl.v < 0.5d ? hsl.v * (1 + hsl.s) : (hsl.v + hsl.s) - (hsl.v * hsl.s);
min = (hsl.v * 2d) - max;
Color c = Color.FromArgb(255, (int)(255 * RGBChannelFromHue(min, max,h + 1 / 3d)),
(int)(255 * RGBChannelFromHue(min, max,h)),
(int)(255 * RGBChannelFromHue(min, max,h - 1 / 3d)));
return c;
}
static double RGBChannelFromHue(double m1, double m2, double h)
{
h = (h + 1d) % 1d;
if (h < 0) h += 1;
if (h * 6 < 1) return m1 + (m2 - m1) * 6 * h;
else if (h * 2 < 1) return m2;
else if (h * 3 < 2) return m1 + (m2 - m1) * 6 * (2d / 3d - h);
else return m1;
}
Do not use the built-in GetBrightness method! It returns the same value (0.5f) for red, magenta, cyan, blue and yellow (!). This is better:
// color brightness as perceived:
float getBrightness(Color c)
{ return (c.R * 0.299f + c.G * 0.587f + c.B *0.114f) / 256f; }

System.Drawing.Color is a value type, which are almost always made immutable, especially in frameworks. That's why you can't setHue on it, you can only construct a new value type with fields you need.
So, if you have a function that will give you RGB values for your HSB values, you can do it like this
Color oldColor = ...;
int red, green, blue;
FromHSB(oldColor.GetHue(), oldColor.GetSaturation(), oldColor.GetBrightness(), out red, out green out blue);
Color newColor = Color.FromArgb(oldColor.A, red, green, blue);
where FromHSB looks like this
void FromHSB(float hue, float saturation, float brightness, out int red, out int green, out int blue)
{
// ...
}

How to change color hue in XNA?

I have a color of class Microsoft.Xna.Framework.Color. How can I change its hue (or get a new color with slightly different hue). Should I convert it to System.Drawing.Color, then somehow change it and convert back? I can't find any useful information on this anywhere.
EDIT
Example:
I have red color R:255, G:0, B:0. Now I want to get slightly more orange color. Then if I get this color and transform it again I'll get even more orange color, then after some transformations I'll go to yellow, green etc. I don't know exact values of ARGB of each color and I don't need them. I just need to change hue of a color by some factor (for example 10 degrees).

You should use the A R G B properties and change the values to get different nyansers.
For example:
Color color = new Color(0,0,0);
//Then you can change the argb properties:
color.A = 10;
color.R = 15;
color.G = 9;
color.B = 25;
If I understand you need something like this:
public static class Utilities
{
public static void Increase(this Color color, int value)
{
if(color.R >= color.G && color.R >= color.B)
color.R += value;
else if(color.G >= color.R && color.G >= color.B)
color.G += value;
else
color.B += value;
}
public static void Decrease(this Color color, int value)
{
if(color.R <= color.G && color.R <= color.B)
color.R -= value;
else if(color.G <= color.R && color.G <= color.B)
color.G -= value;
else
color.B -= value;
}
}
Then:
Color myColor = new Color(10,0,0);
myColor.Increase(10);
//or
myColor.Decrease(10);

according to this documentation, you can pass whatever RGB(A) values you want into the XNA color class constructor. You can also use the R, B, and G properties to change them afterwards
example:
Color myColor = new Color(150, 100, 100);
myColor.R = 200
that example will change a red to a slightly deeper red.
An example of making a color go from Red to orange to yellow to green would be
Color myColor = new Color(255, 0, 0);
for(int i=0; i<255; i++)
{
myColor.R--;
myColor.G++
}
Red and Green make yellow, so higher numbers of red will make it redder, higher numbers of green will make it greener. same of both numbers make it redder.
You can change color incrementally in other ways too, so long as you know how the primary colors of light work.
You're never ever going to find a function called Color.MakeRedder() or Color.MakeGreener() It will always focus on some sort of mathmatical representation of the color, (RBG is most common but there are other representations)
If you want to convert Hue to RBG Here is a guide on how to do it
What would probably be easiest is to keep track of a System.Drawing.Color class as your base color class, and modify your XNA Color Class based on your System.Drawing.Color class accordingly.
If you want to get really adventurous, you can see if it is possible to make a class that extends(inherits from) Microsoft.Xna.Framework.Color, override the R, G, and B properties, so that they are based off of an underlying System.Drawing.Color object

I did some research and found this post which has C++ code:
http://www.cs.rit.edu/~ncs/color/t_convert.html
I've modified the code to be C#, to have an IncreaseHueBy method, and to fix a few bugs:
public static void IncreaseHueBy(ref Color color, float value, out float hue)
{
float h, s, v;
RgbToHsv(color.R, color.G, color.B, out h, out s, out v);
h += value;
float r, g, b;
HsvToRgb(h, s, v, out r, out g, out b);
color.R = (byte)(r);
color.G = (byte)(g);
color.B = (byte)(b);
hue = h;
}
static void RgbToHsv(float r, float g, float b, out float h, out float s, out float v)
{
float min, max, delta;
min = System.Math.Min(System.Math.Min(r, g), b);
max = System.Math.Max(System.Math.Max(r, g), b);
v = max; // v
delta = max - min;
if (max != 0)
{
s = delta / max; // s
if (r == max)
h = (g - b) / delta; // between yellow & magenta
else if (g == max)
h = 2 + (b - r) / delta; // between cyan & yellow
else
h = 4 + (r - g) / delta; // between magenta & cyan
h *= 60; // degrees
if (h < 0)
h += 360;
}
else
{
// r = g = b = 0 // s = 0, v is undefined
s = 0;
h = -1;
}
}
static void HsvToRgb(float h, float s, float v, out float r, out float g, out float b)
{
// Keeps h from going over 360
h = h - ((int)(h / 360) * 360);
int i;
float f, p, q, t;
if (s == 0)
{
// achromatic (grey)
r = g = b = v;
return;
}
h /= 60; // sector 0 to 5
i = (int)h;
f = h - i; // factorial part of h
p = v * (1 - s);
q = v * (1 - s * f);
t = v * (1 - s * (1 - f));
switch (i)
{
case 0:
r = v;
g = t;
b = p;
break;
case 1:
r = q;
g = v;
b = p;
break;
case 2:
r = p;
g = v;
b = t;
break;
case 3:
r = p;
g = q;
b = v;
break;
case 4:
r = t;
g = p;
b = v;
break;
default: // case 5:
r = v;
g = p;
b = q;
break;
}
}
I tested it by using a value of 1 to increase the hue by 1 every frame and it worked fairly well. Notice there may be some rounding errors.

"Colourizing" a Bitmap in .NET

If you have a System.Drawing.Bitmap instance that contains a greyscale image, is there a built in way to "colourize" it with the influence of another colour?
For example, if you had a black and white (greyscale) picture of a coffee mug and you wanted to create separate images of red, green and purple versions programmatically.

I don't have a code example to give but here's a way to do this. Convert each pixel from RGB to HSV and change the Hue and Saturation component on each pixel. The Hue controls the Color. The Value should stay the same. The result will be a Bitmap with the same lightness and darkness but with a different color.
Edit: here's an example. Notice the Hue and Saturation update.
public static Color ColorFromAhsb(int a, float h, float s, float b)
{
if (0 > a || 255 < a)
{
throw new Exception("a");
}
if (0f > h || 360f < h)
{
throw new Exception("h");
}
if (0f > s || 1f < s)
{
throw new Exception("s");
}
if (0f > b || 1f < b)
{
throw new Exception("b");
}
if (0 == s)
{
return Color.FromArgb(a, Convert.ToInt32(b * 255),
Convert.ToInt32(b * 255), Convert.ToInt32(b * 255));
}
float fMax, fMid, fMin;
int iSextant, iMax, iMid, iMin;
if (0.5 < b)
{
fMax = b - (b * s) + s;
fMin = b + (b * s) - s;
}
else
{
fMax = b + (b * s);
fMin = b - (b * s);
}
iSextant = (int)Math.Floor(h / 60f);
if (300f <= h)
{
h -= 360f;
}
h /= 60f;
h -= 2f * (float)Math.Floor(((iSextant + 1f) % 6f) / 2f);
if (0 == iSextant % 2)
{
fMid = h * (fMax - fMin) + fMin;
}
else
{
fMid = fMin - h * (fMax - fMin);
}
iMax = Convert.ToInt32(fMax * 255);
iMid = Convert.ToInt32(fMid * 255);
iMin = Convert.ToInt32(fMin * 255);
switch (iSextant)
{
case 1:
return Color.FromArgb(a, iMid, iMax, iMin);
case 2:
return Color.FromArgb(a, iMin, iMax, iMid);
case 3:
return Color.FromArgb(a, iMin, iMid, iMax);
case 4:
return Color.FromArgb(a, iMid, iMin, iMax);
case 5:
return Color.FromArgb(a, iMax, iMin, iMid);
default:
return Color.FromArgb(a, iMax, iMid, iMin);
}
}
private void Form1_Load(object sender, EventArgs e)
{
var bmp = new Bitmap("c:\\bw.bmp");
foreach (int y in Enumerable.Range(0, bmp.Height))
{
foreach (int x in Enumerable.Range(0,bmp.Width))
{
var p = bmp.GetPixel(x, y);
var h = p.GetHue();
var c = ColorFromAhsb(p.A, p.GetHue() + 200, p.GetSaturation() + 0.5f, p.GetBrightness());
bmp.SetPixel(x, y, c);
}
}
pictureBox1.Image = bmp;
//bmp.Dispose();
}

If it's an 8 bit image, you can just use a different the palette (Image.Palette). That's essentially a lookup table that assigns a Color value to each possible pixel byte value. Much faster than changing all pixels in a loop.

See here
I have used this in the past. You are wanting to look specifically at ToSepia.
You may need to deconstruct this a bit but it has worked for me.

I'd create a copy of the original image and them put a separate semi transparent image of the desired color of the top.
Update: see example at http://www.codeproject.com/KB/cs/Merge_Images_in_C_.aspx

I am unsure of a built in way but, if you represent each colour as a float rather than a byte (255 becomes 1 - full intensity), multiplying the each channel with your desired colour should give the effect you are talking about.
(1,1,1) "white" * (1,0,0) "red" = (1,0,0) "red"
(0.5,0.5, 0.5) "grey" * (0,1,0) "green" = (0,0.5,0) "dark green"
You do need to apply this per pixel though.

How to Convert RGB Color to HSV?

How can I convert a RGB Color to HSV using C#?
I've searched for a fast method without using any external library.

Note that Color.GetSaturation() and Color.GetBrightness() return HSL values, not HSV.
The following code demonstrates the difference.
Color original = Color.FromArgb(50, 120, 200);
// original = {Name=ff3278c8, ARGB=(255, 50, 120, 200)}
double hue;
double saturation;
double value;
ColorToHSV(original, out hue, out saturation, out value);
// hue = 212.0
// saturation = 0.75
// value = 0.78431372549019607
Color copy = ColorFromHSV(hue, saturation, value);
// copy = {Name=ff3278c8, ARGB=(255, 50, 120, 200)}
// Compare that to the HSL values that the .NET framework provides:
original.GetHue(); // 212.0
original.GetSaturation(); // 0.6
original.GetBrightness(); // 0.490196079
The following C# code is what you want. It converts between RGB and HSV using the algorithms described on Wikipedia. The ranges are 0 - 360 for hue, and 0 - 1 for saturation or value.
public static void ColorToHSV(Color color, out double hue, out double saturation, out double value)
{
int max = Math.Max(color.R, Math.Max(color.G, color.B));
int min = Math.Min(color.R, Math.Min(color.G, color.B));
hue = color.GetHue();
saturation = (max == 0) ? 0 : 1d - (1d * min / max);
value = max / 255d;
}
public static Color ColorFromHSV(double hue, double saturation, double value)
{
int hi = Convert.ToInt32(Math.Floor(hue / 60)) % 6;
double f = hue / 60 - Math.Floor(hue / 60);
value = value * 255;
int v = Convert.ToInt32(value);
int p = Convert.ToInt32(value * (1 - saturation));
int q = Convert.ToInt32(value * (1 - f * saturation));
int t = Convert.ToInt32(value * (1 - (1 - f) * saturation));
if (hi == 0)
return Color.FromArgb(255, v, t, p);
else if (hi == 1)
return Color.FromArgb(255, q, v, p);
else if (hi == 2)
return Color.FromArgb(255, p, v, t);
else if (hi == 3)
return Color.FromArgb(255, p, q, v);
else if (hi == 4)
return Color.FromArgb(255, t, p, v);
else
return Color.FromArgb(255, v, p, q);
}

Have you considered simply using System.Drawing namespace? For example:
System.Drawing.Color color = System.Drawing.Color.FromArgb(red, green, blue);
float hue = color.GetHue();
float saturation = color.GetSaturation();
float lightness = color.GetBrightness();
Note that it's not exactly what you've asked for (see differences between HSL and HSV and the Color class does not have a conversion back from HSL/HSV but the latter is reasonably easy to add.

The EasyRGB has many color space conversions. Here is the code for the RGB->HSV conversion.

There's a C implementation here:
http://www.cs.rit.edu/~ncs/color/t_convert.html
Should be very straightforward to convert to C#, as almost no functions are called - just calculations.
found via Google

This is the VB.net version which works fine for me ported from the C code in BlaM's post.
There's a C implementation here:
http://www.cs.rit.edu/~ncs/color/t_convert.html
Should be very straightforward to convert to C#, as almost no functions are called - just > calculations.
Public Sub HSVtoRGB(ByRef r As Double, ByRef g As Double, ByRef b As Double, ByVal h As Double, ByVal s As Double, ByVal v As Double)
Dim i As Integer
Dim f, p, q, t As Double
If (s = 0) Then
' achromatic (grey)
r = v
g = v
b = v
Exit Sub
End If
h /= 60 'sector 0 to 5
i = Math.Floor(h)
f = h - i 'factorial part of h
p = v * (1 - s)
q = v * (1 - s * f)
t = v * (1 - s * (1 - f))
Select Case (i)
Case 0
r = v
g = t
b = p
Exit Select
Case 1
r = q
g = v
b = p
Exit Select
Case 2
r = p
g = v
b = t
Exit Select
Case 3
r = p
g = q
b = v
Exit Select
Case 4
r = t
g = p
b = v
Exit Select
Case Else 'case 5:
r = v
g = p
b = q
Exit Select
End Select
End Sub

I've ended up here by having the same need.
Bellow I'm sharing the best and simpler solution I could find so far.
This is a modified answer from Greg's (found here); but with a humbler and understandable code.
For those who are learning I've added a few references that are worth checking for the sake of understanding.
References
"Lukas Stratmann" HSV Model Tool (Incl. Other Model Systems: CMY / CMYK / HSL)
"The HSV Color Model in Graphic Design"
"Formula to Determine Perceived Brightness of RGB Color"
Fastest Formula to Get Hue from RGB
"Color Conversion Algorithms"
"Program to Change RGB color model to HSV color model"
"RGB to HSV Color Conversion Algorithm"
"RGB to HSV Color Space Conversion (C)"
"How to Convert RGB Color to HSV"
Code
/// <summary> Convert RGB Color to HSV. </summary>
/// <param name="color"></param>
/// <returns> A double[] Containing HSV Color Values. </returns>
public double[] rgbToHSV(Color color)
{
double[] output = new double[3];
double hue, saturation, value;
int max = Math.Max(color.R, Math.Max(color.G, color.B));
int min = Math.Min(color.R, Math.Min(color.G, color.B));
hue = color.GetHue();
saturation = (max == 0) ? 0 : 1d - (1d * min / max);
value = max / 255d;
output[0] = hue;
output[1] = saturation;
output[2] = value;
return output;
}

FIRST: make sure you have a color as a bitmap, like this:
Bitmap bmp = (Bitmap)pictureBox1.Image.Clone();
paintcolor = bmp.GetPixel(e.X, e.Y);
(e is from the event handler wich picked my color!)
What I did when I had this problem a whilke ago, I first got the rgba (red, green, blue and alpha) values.
Next I created 3 floats: float hue, float saturation, float brightness. Then you simply do:
hue = yourcolor.Gethue;
saturation = yourcolor.GetSaturation;
brightness = yourcolor.GetBrightness;
The whole lot looks like this:
Bitmap bmp = (Bitmap)pictureBox1.Image.Clone();
paintcolor = bmp.GetPixel(e.X, e.Y);
float hue;
float saturation;
float brightness;
hue = paintcolor.GetHue();
saturation = paintcolor.GetSaturation();
brightness = paintcolor.GetBrightness();
If you now want to display them in a label, just do:
yourlabelname.Text = hue.ToString;
yourlabelname.Text = saturation.ToString;
yourlabelname.Text = brightness.ToString;
Here you go, you now have RGB Values into HSV values :)
Hope this helps