This is indeed outside of -drawRect, and it's a context I create myself, like
so:
// returns a new 'abstract' graphics context to draw in:
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
bitmapBytesPerRow = (pixelsWide * 4);
bitmapByteCount = (bitmapBytesPerRow * pixelsHigh);
colorSpace = CGColorSpaceCreateDeviceRGB();
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
fprintf (stderr, "Memory not allocated!");
return NULL;
}
context = CGBitmapContextCreate (bitmapData,
pixelsWide,
pixelsHigh,
8,
// bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast);
if (context== NULL)
{
free (bitmapData);
fprintf (stderr, "Context not created!");
return NULL;
}
CGColorSpaceRelease( colorSpace );
CGContextSetAllowsAntialiasing(context, YES);
CGContextSetShouldAntialias(context, YES);
return context;
Rainer
On Oct 4, 2010, at 11:15 , David Duncan wrote:
> On Oct 4, 2010, at 11:04 AM, Rainer Standke wrote:
>
>> wondering how to clear a context. I'm using this:
>>
>> CGContextClearRect(context, drawingRect);
>>
>> But yet, afetr I do that, and then start to draw something new, I get
>> remnants of the previous content of the context.
>
>
> Where are you calling this? About the only thing I know of that might cause
> this is trying to call UIGraphicsGetCurrentContext() from outside of
> -drawRect: (in which case unless you've pushed or started your own context
> you get back NULL, which CG ignores).
> --
> David Duncan
>
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