BufferPainter.h:

struct SpanSource {
	int kind;
	SpanSource(){
		kind = IMAGE_OPAQUE;
	}
	virtual void Get(RGBA *span, int x, int y, unsigned len) = 0;
	virtual ~SpanSource() {}
};

Fillers.cpp:

void SpanFiller::Render(int val, int len)
{
	if(val == 0) {
		t += len;
		s += len;
		return;
	}
	if(alpha != 256)
		val = alpha * val >> 8;

	if(val == 256) {
		if(ss->kind==IMAGE_OPAQUE) memcpy(t,s,len*sizeof(RGBA)); // apex_memcpy() would be even faster
		else{
			for(int i = 0; i < len; i++) {
				if(s[i].a == 255)
					t[i] = s[i];
				else
					AlphaBlend(t[i], s[i]);
			}
		}
		t += len;
		s += len;
	}
	else {
		const RGBA *e = t + len;
		while(t < e)
			AlphaBlendCover8(*t++, *s++, val);
	}
}

Painter/Image.cpp:


struct PainterImageSpan : SpanSource, PainterImageSpanData {
	LinearInterpolator interpolator;

	PainterImageSpan(const PainterImageSpanData& f)
	:	PainterImageSpanData(f) {
		interpolator.Set(xform);
		kind = image.GetKindNoScan(); // Add this
	}