Image processing
View Patent ↗The present invention relates to methods and apparatus for interpolation of images, and in a particular example to de-interlacing of video signals using spatial interpolation. The present invention discloses a method for measuring the slope of a picture portion in which picture gradients are calculated from said selected pixel values and the slope measurement being derived from said gradient values. The invention also discloses a method of spatial interpolation of an array of pixel values, in which interpolated values are dependent upon the measurement of the slope associated with said array. Non-integer slopes can easily be accommodated with the method of the invention.
1. A spatial interpolator comprising:
an input adapted to receive a plurality of input pixel values;
one or more filters for deriving horizontal (Gx) and vertical (Gy) picture gradients from said input pixels;
a first multiplier for multiplying said horizontal (Gx) picture gradient by said vertical (Gy) picture gradient to form a first product (Gy·Gx);
a first smoothing filter operating on said first product (Gy·Gx) to form Filtered(Gy·Gx);
a second multiplier for multiplying said horizontal (Gx) picture gradient by itself to form a second product (Gx·Gx);
a second smoothing filter operating on said second product (Gx·Gx) to form Filtered(Gx·Gx);
a processor for deriving a slope measurement associated with the input pixels from said picture gradients according to:
slope=Filtered( Gy·Gx )/Filtered Gx·Gx ); and
a processor for generating an interpolated output in which interpolated values are dependent upon the slope measurement of the slope associated with said array.
2. A spatial interpolator as claimed in claim 1 further comprising: a vertical filter for deriving a vertical interpolation value from said input pixels, and a processor for producing a correction value dependent on said slope measurement, wherein the interpolated output is a combination of the vertical interpolation and the correction value.
3. A spatial interpolator as claimed in claim 1 comprising one or more filters for deriving a measure of spatial activity of said input pixels, the slope measurement being dependent on said measure of spatial picture activity.