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CGContextSetLineWidth / performance issues

Hi

My code, below, renders a complex path (around 800 points) using quartz, and works pretty well when CGContextSetLineWidth(ctx, _strokewidth) is set to 1.0f. However as I increase _strokewidth then performance becomes significantly worse, infact unusable. Ultimately I want to apply CI filters and so forth...

Is there an optimization route for rendering lines >1.0f ?

Thanks

Nick


- (void)render:(void*)dst data:(void*)data
{
    float w             = _width;
    float h             = _height;
    Float32* buffer     = nil;
    UInt32 size         = nil;
    BufferRecordPtr br  = (BufferRecordPtr)data;
    buffer              = br->buffer;
    size                = br->size;

    CGContextRef ctx = (CGContextRef)dst;
    {
        CGContextSetRGBFillColor(ctx, 0.0, 0.0, 0.0, 1.0);
        CGContextFillRect(ctx, CGRectMake(0, 0, w, h));

if(buffer != nil && size != nil)
{
float xstep = w / size;
CGContextSetShouldAntialias(ctx, _antialias );
CGContextSetLineWidth(ctx, _strokewidth);
CGContextSetRGBStrokeColor(ctx, [_forecolor redComponent], [_forecolor greenComponent], [_forecolor blueComponent], _alpha);
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, 0.0, (float)((buffer[0]*_size)/ _scale)+h/2);
UInt32 i;
for (i = 1; i < size; i+=_resolution){
CGContextAddLineToPoint(ctx, (float)xstep * i, (float)((buffer[i]*_size)/_scale)+h/2);
}
CGContextStrokePath(ctx);
}
}
}


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