objective c - How to fade between define colors with a dependent variable returning UIColor -

i want create function, in format shown in code below, fade between defined colors. purpose of function change color of table view cell depending on when data created; nsdate. function should consider time of day; 2015-07-07t12:00:00 have same color 2015-07-06t12:00:00.

@implementation nsdate (color_)  - (uicolor *)daynightcolorbytimeofday {  }  @end 

the colors want "fade" between these:

• 12a #0525ff
• 6a #fff199
• 12p #ffd005
• 6p #059cff
• and 12a.

an example date passed function, datevalue = 3pm, return color between 2 colors, 12p , 6p. don't want animate.

each cell in table represents instance of array:

array {   ...   nsstring title,   nsdate date   ... }; 

the data in array.date set [nsdate date]. tell self, data type of nsdate, defendant variable.

the answer contains few ideas. first interpolation of colors. rgb representation can interpolated interpolating components, this:

// take 2 bounding colors , answer 1 pct distance between them - (uicolor *)colorbetween:(uicolor *)colora and:(uicolor *)colorb distance:(cgfloat)pct {     cgfloat ar, ag, ab, aa;     [colora getred:&ar green:&ag blue:&ab alpha:&aa];      cgfloat br, bg, bb, ba;     [colorb getred:&br green:&bg blue:&bb alpha:&ba];      cgfloat rr = (1.0-pct)*ar + pct*br;     cgfloat rg = (1.0-pct)*ag + pct*bg;     cgfloat rb = (1.0-pct)*ab + pct*bb;     cgfloat ra = (1.0-pct)*aa + pct*ba;      return [uicolor colorwithred:rr green:rg blue:rb alpha:ra]; } 

we need interpolate times, can done approximately representing times minutes past midnight...

- (nsinteger)minutessincemidnightofdate:(nsdate *)date {      nsdatecomponents *components = [[nscalendar currentcalendar] components:nsintegermax fromdate:date];     [components sethour:0];     [components setminute:0];     [components setsecond:0];      nsdate *midnight = [[nscalendar currentcalendar] datefromcomponents:components];      nsdatecomponents *diff = [[nscalendar currentcalendar] components:nscalendarunitminute fromdate:midnight todate:date options:0];      return [diff minute]; } 

we need represent parameters interpolation, done here directly possible given in question...

// macro convert hex value uicolor #define uicolorfromrgb(rgbvalue) \     [uicolor colorwithred:((float)((rgbvalue & 0xff0000) >> 16))/255.0 \                     green:((float)((rgbvalue & 0x00ff00) >>  8))/255.0 \                      blue:((float)((rgbvalue & 0x0000ff) >>  0))/255.0 \                     alpha:1.0] 

now, work, find times (in minutes past midnight) before , after given time, colors corresponding times, interpolate colors proportion matching temporal distance between before , after times.

- (uicolor *)colorfordate:(nsdate *)date {     // bounds of interpolation here     nsarray *wheel = @[ @[ @0,    uicolorfromrgb(0x0525ff) ],                         @[ @360,  uicolorfromrgb(0xfff199) ],                         @[ @720,  uicolorfromrgb(0xffd005) ],                         @[ @1080, uicolorfromrgb(0x059cff) ],                         @[ @1440, uicolorfromrgb(0x0525ff) ]];      nsinteger m = [self minutessincemidnightofdate:date];      // find index in wheel minute bound exceeds our date's minutes (m)     nsinteger wheelindex = 0;     (nsarray *pair in wheel) {         nsinteger timeposition = [pair[0] intvalue];         if (m < timeposition) {             break;         }         wheelindex++;     }      // wheelindex in 1..4, pair of bounds @ wheelindex     // , preceding pair (-1).     nsarray *priorpair = wheel[wheelindex-1];     nsarray *pair = wheel[wheelindex];      cgfloat priorminutes = [priorpair[0] intvalue];     cgfloat minutes = [pair[0] intvalue];      // how far between bounds pairs     cgfloat minutespct = ((float)m - priorminutes) / (minutes - priorminutes);      // , colors bounds pair     uicolor *priorcolor = priorpair[1];     uicolor *color = pair[1];      // call color interpolation     return [self colorbetween:priorcolor and:color distance:minutespct]; }