graphical APIs

[technorobbo]

Technorobbo, would you please explain the following:

1) Const PHMinus1 = picHeight - 1: why -1?


2) StretchBlt Me.hdc, Pt(0).X, Pt(0).Y, Pt(1).X - Pt(0).X + 1, 2, Shdc, 0, PHMinus1 * i, picWidth, 1, vbSrcCopy: why +1?
3) StretchBlt Me.hdc, Pt(0).X, Pt(0).Y, Pt(1).X - Pt(0).X + 1, 2, Shdc, 0, PHMinus1 * i, picWidth, 1, vbSrcCopy: why 2?

Thanks again.

1) it's the difference between zero based coordinates and one-based pixel width
2) same answer: 1-2=1 but it's 2 digits

3)sometimes scanlines appear if you don't - I've found it a best practice