my colour bitmap is only black and white in drawRect (iPhone) - iphone

Question

I want to preserve previous drawing in drawRect (the system clears it down each time) and it seems that the way to go is to use a bitmap context and sure enough, this works except that now my colour is gone leaving only black and white instead.
Here is my "static" context
-(id)initWithCoder:(NSCoder *)aDecoder {
...
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
contextRef = CGBitmapContextCreate(NULL,
320,
640,
8,
320*4,
colorSpace,
kCGImageAlphaPremultipliedLast);
...
}
and here is my replacement context:
-(void)drawRect:(CGRect)rect {
myDrawRoutine();
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, rect, CGBitmapContextCreateImage(contextRef));
}
And this is the draw routine's guts:
...
// CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRef context = contextRef;
if( !(context) )
return;
CGContextSetFillColor(context, CGColorGetComponents([co CGColor]));
CGContextSetStrokeColor(context, CGColorGetComponents([co CGColor]));
CGContextFillEllipseInRect(context, CGRectMake((*i)->x,
(*i)->y,
(*i)->diam,
(*i)->diam));
...
}

Answer 1

Thanks tonclon
That has made a hell of an increase in speed :)
But it still draws in black and white :(
Here is the above code + modifications...
Here is my "static context":
-(id)initWithCoder:(NSCoder *)aDecoder {
...
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
contextRef = CGBitmapContextCreate(NULL,
320,
640,
8,
320*4,
colorSpace,
kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorSpace);
cglayer = CGLayerCreateWithContext(contextRef, CGSizeMake(320.0f, 640.0f), NULL);
contextRef = CGLayerGetContext(cglayer);
...
}
and here is my "replacement context" i.e. the cglayer is used instead (the context is no longer replaced).
-(void)drawRect:(CGRect)rect {
for(std::vector<Body*>::iterator i = bodyVec.begin(); i < bodyVec.end(); ++i)
move(i);
CGContextRef context = UIGraphicsGetCurrentContext();
// CGContextDrawImage(context, rect, CGBitmapContextCreateImage(contextRef));
CGContextDrawLayerInRect(context, rect, cglayer);
}
(The "draw routine's guts" remain the same.)

Answer 2

At last! Thanks to this thread
Extracting rgb from UIColor
I got the answer - use CGContextSetRGBFillColor instead and then feed it with the RGB from CGColorGetComponents indirectly.
CGColorRef color = [co CGColor];
int numComponents = CGColorGetNumberOfComponents(color);
CGFloat red;
CGFloat green;
CGFloat blue;
CGFloat alpha;
if (numComponents == 4)
{
const CGFloat *components = CGColorGetComponents(color);
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
}
// CGContextSetFillColor(context, CGColorGetComponents([co CGColor]));
// CGContextSetStrokeColor(context, CGColorGetComponents([co CGColor]));
CGContextSetRGBFillColor(context, red, green, blue, alpha);
CGContextSetRGBStrokeColor(context, red, green, blue, alpha);
CGContextFillEllipseInRect(context, CGRectMake((*i)->x,
(*i)->y,
(*i)->diam,
(*i)->diam));
}