Apparatus and method for alpha blending of digital images

A method for performing alpha blending calculations on a first digital image value X and a second digital image value Y according to a digital alpha (α) value having a fractional part of n digits and having a most significant bit of α1 and a least significant bit of αn−1 and wherein the order of αi is i, comprising:

• receiving the first and second digital image values;
• receiving the α value;
• selecting the first digital value responsive to a logical high of the bit value, αi, of α otherwise selecting the second digital value responsive to a logical low of the bit value, αi, of α, the selected first or second digital value being a selected digital value;
• shifting the selected digital value in a shifter left according to the order of the bit values, αi, of α to generate a plurality of left shifted digital values;
• and
• adding the plurality of left-shifted digital values from the shifters to generate a result, R.

An apparatus for performing alpha blending calculations on a first digital image value and a second digital image value according to a digital alpha (α) value having a fractional part of n digits and having a most significant bit of α1 and a least significant bit of αn−1 and wherein the order of αi is related to an ith digit of α, comprising:

• a plurality of means for selecting the first digital value responsive to a logical high of the bit value, αi, of α, otherwise selecting the second digital value responsive to a logical low of the bit value, αi, of α, the selected first or second digital value being a selected digital value;
• means for shifting the selected digital value left according to the order of the bit values, αi, of α to generate a plurality of left shifted digital values;
• and
• means for adding the plurality of left-shifted digital values to generate a result, R.

A computer program product stored on a computer readable medium embodying a program of instructions executable by a machine to perform method steps for performing alpha blending calculations on a first digital image value X and a second digital image value Y according to a digital alpha (α) value having a fractional part of n digits and having a most significant bit of α1 and a least significant bit of αn−1 and wherein the order of αi is i, said product being operative to execute a method comprising:

• receiving the first and second digital image values;
• receiving the α value;
• selecting the first digital value responsive to a logical high of the bit value, αi, of α, otherwise selecting the second digital value responsive to a logical low of the bit value, αi, of α, the selected first or second digital value being a selected digital value;
• shifting the selected digital value in a shifter left according to the order of the bit values, αi, of α to generate a plurality of left shifted digital values;
• and
• adding the plurality of left-shifted digital values from the shifter to generate a result, R.