Alpha blending calculator

An alpha blending calculator for executing an alpha blending calculation in accordance with digital data X, Y, and .alpha. each composed of a plurality of bits, the alpha blending calculator comprising:

• a plurality of selection means, each of the selection means selecting one of X or Y in accordance with one of the plurality of bits of the digital data .alpha.;
• and
• calculation means for shifting outputs of the plurality of selection means by a predetermined number of bits, respectively, and for calculating a sum of the shifted outputs, the calculation means comprising:
• first level to Nth level first adding means;
• and second adding means, connected to outputs of the Nth level first adding means, for executing a multi-bit addition, wherein each of the first level to the Nth level first adding means:
• (a) receives a plurality of stages of data,
• (b) classifies the plurality of stages of data into at least one quotient group which includes a predetermined number of stages of data and a remainder group including a number of stages of data which is smaller than the predetermined number,
• (c) calculates a sum of the predetermined number of stages of data and a carry for the quotient group, and
• (d) outputs the sum and the carry to the next level first adding means, and outputs the stages of data in the remainder group to the next level first adding means if the number of stages in the remainder group is greater than zero,
• wherein the outputs of the plurality of selection means are input as the plurality of stages of data to the first level first adding means, and
• the outputs of the Nth level first adding means consist of a sum and a carry.