If a vertex (x1, Y1) is rotated to (X2, Y2), the corresponding angle is rotated from θ 1 to θ 1 + θ 2.
Sin θ 1 = Y1/SQRT (x1 * X1 + Y1 * Y1)
COS θ 1 = x1/SQRT (x1 * X1 + Y1 * Y1)
Sin (θ 1 + θ 2) = sin (θ 1) * Cos (θ 2) + cos (θ 1) * sin (θ 2) = Y2/SQRT (X2 * X2 + y2 * Y2) Cos (θ 1 + θ 2) = cos (θ 1) * Cos (θ 2)-sin (θ 1) * sin (θ 2) = x2/SQRT (X2 * X2 + y2 * Y2) according to the above push y2 = x1 * sin (θ 2) + Y1 * Cos (θ 2 );
X2 = x1 * Cos (θ 2)-Y1 * sin (θ 2 );
Code example X1 = (INT) x; x2 = X1 + 1; Y1 = int (y); y2 = Y1 + 1; dx = float (x-x1); dx1 = 1.0-dx; DY = float (y-y1); dy1 = 1.0-dy; m_trespixelarray [I] [J]. rgbblue = m_toripixelarray [Y1] [X1]. rgbblue * dx1 * dy1 + m_toripixelarray [Y1 + 1] [X1]. rgbblue * DX * dy1 + m_toripixelarray [Y1] [X1 + 1]. rgbblue * dx1 * dy + m_toripixelarray [Y1 + 1] [X1 + 1]. rgbblue * DX * dy + 0.5;