Method and apparatus for image scaling
A source image with an input vertical resolution and an input horizontal resolution is received using an input clock signal. An intermediate image with an output vertical resolution and the input horizontal resolution is generated using an intermediate clock signal by scaling the source image. An output image with the output vertical resolution and an output horizontal resolution is generated using an output clock signal by scaling the intermediate image. The frequency of the intermediate clock signal is equal to the frequency of the output clock signal multiplied by the ratio of the input horizontal resolution to the output horizontal resolution.
1. A method for image scaling, comprising the steps of:
receiving a source image with an input vertical resolution and an input horizontal resolution using an input clock signal;
generating an intermediate image with an output vertical resolution and the input horizontal resolution using an intermediate clock signal by scaling the source image; and
generating an output image with the output vertical resolution and an output horizontal resolution using an output clock signal by scaling the intermediate image;
wherein a frequency of the intermediate clock signal is equal to a frequency of the output clock signal multiplied by a ratio of the input horizontal resolution to the output horizontal resolution, the intermediate clock signal and the output clock signal being generated by a phase-locked loop, and wherein the phase-locked loop has two frequency dividers for outputting the intermediate clock signal and the output clock signal, respectively.
2. The method for image scaling as claimed in claim 1 , wherein a ratio of factors of the two frequency dividers is equal to the ratio of the input horizontal resolution to the output horizontal resolution.
3. The method for image scaling as claimed in claim 1 , wherein the source image and the output image have the same or different aspect ratios.
4. The method for image scaling as claimed in claim 1 , wherein the generating steps are scaling up or scaling down the images.
5. An image scaler for scaling a source image into an output image via an intermediate image, wherein the source image has an input vertical resolution and an input horizontal resolution, and is received using an input clock signal, the intermediate image has an output vertical resolution and the input horizontal resolution, and is generated using an intermediate clock signal, and the output image has the output vertical resolution and an output horizontal resolution, and is output using an output clock signal, the image scaler characterized by comprising:
a phase-locked loop with two frequency dividers for outputting the intermediate clock signal and output clock signal, respectively, wherein a frequency of the intermediate clock signal is equal to a frequency of the output clock signal multiplied by a ratio of the input horizontal resolution to the output horizontal resolution.
6. The image scaler as claimed in claim 5 , wherein a ratio of factors of the two frequency dividers is equal to the ratio of the input horizontal resolution to the output horizontal resolution.
7. The image scaler as claimed in claim 5 , wherein the source image and the output image have the same or different aspect ratios.