4 Colors gradient logic needed
I need to create 4 color gradient logic. One of the posts gave me the pattern to calculate 4 color gradient. However I am having difficutlties to implement it.
I am able to calculate color of point E ( middle one) however I do not know how to develop the gradient from it
MY code
COLORREF NewColor = RGB(255,0,0);
COLORREF NewColor2 = RGB(0,255,0);
COLORREF NewColor3 = RGB(0,0,255);
COLORREF NewColor4 = RGB(255,255,0);
red_low = GetRValue(NewColor);
blue_low = GetBValue(NewColor);
green_low = GetGValue(NewColor);
red_high = GetRValue(NewColor2);
green_high= GetGValue(NewColor2);
blue_high = GetBValue(NewColor2);
red_low2 = GetRValue(NewColor3);
blue_low2 = GetBValue(NewColor3); // divide the difference in colours by the number of steps
green_low2 = GetGValue(NewColor3);
red_high2 = GetRValue(NewColor4);
green_high2 = GetGValue(NewColor4); // divide the difference in colours by the number of steps
blue_high2 = GetBValue(NewColor4);
double distance_a = sqrt((double)((0-W)^2+(0-H/2)^2));
double distance_b = sqrt((double)((350-W/2)^2+(0-H/2)^2));
double distance_c =开发者_运维问答 sqrt((double)((350-W/2)^2+(100-H/2)^2));
double distance_d = sqrt((double)((0-W/2)^2+(100-H/2)^2));
double sum_distances = distance_a + distance_b + distance_c + distance_d;
double red = (red_low*distance_a + red_high*distance_b + red_low2*distance_c+ red_high2*distance_d) / sum_distances;
double green = (green_low*distance_a + green_high*distance_b + green_low2*distance_c+ green_high2*distance_d) / sum_distances;
double blue = (blue_low*distance_a + blue_high*distance_b + blue_low2*distance_c+ blue_high2*distance_d) / sum_distances;
COLORREF Color_E= RGB(red,green,blue);
Ane help how to futher code it is appreciated.
Here's code that computes the color at (x,y) given the four corner colors.
#include <vector>
#include <cassert>
#include <windows.h>
using namespace std;
int interpolate(int a, int b, int c, int d, double t, double s)
{
return (int)(a*(1-t)*(1-s) + b*t*(1-s) + c*(1-t)*s + d*t*s);
}
COLORREF interpolateColors(const vector<COLORREF> &cornercolors, int W, int H, int x, int y)
{
assert(cornercolors.size() == 4);
double t = ((double)x)/W;
double s = ((double)y)/H;
return RGB( interpolate(GetRValue(cornercolors[0]), GetRValue(cornercolors[1]), GetRValue(cornercolors[2]), GetRValue(cornercolors[3]), t, s),
interpolate(GetGValue(cornercolors[0]), GetGValue(cornercolors[1]), GetGValue(cornercolors[2]), GetGValue(cornercolors[3]), t, s),
interpolate(GetBValue(cornercolors[0]), GetBValue(cornercolors[1]), GetBValue(cornercolors[2]), GetBValue(cornercolors[3]), t, s) );
}
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