Method and circuit for scaling raster images
View Patent ↗A method is proposed which enables high-resolution raster images to be represented on lower-resolution displays. The method according to the invention selects support points in lines and columns of the original image, which have a smallest possible variation of their distances and approximate the set scaling at least in ranges. Consequently, rational scaling ratios can also be achieved in an advantageous manner. In order to represent fine details of the original image in the scaled image as well, the adjacent pixels of the support points are also incorporated into the calculation of the pixels that are output. Furthermore, a circuit for scaling a raster image in real time is proposed. Moreover, a film scanner having a scaling device in accordance with the method according to the invention is proposed.
1. A method for controlling a display device to display input video images represented by a first number of pixels or subpixels arranged line by line and column by column in an input video signal to the display device which has a display area that displays an output video image having a second number of pixels or subpixels arranged line by line and column by column, wherein the numbers of lines and/or columns of the display area differ from the number of lines and/or columns of the input video images, the method comprising the steps of:
distributing a number of support points, corresponding to a number of pixels or subpixels in the output video image displayed in the display area of the display device, across the lines or columns of the input video image at integer pixel or subpixel distances having a minimum variation from one another, wherein the ratio of the number of support points to the number of pixels or subpixels in a line or column of the input video image correspond to the desired scaling factor; and
selecting or calculating one of a pixel or subpixel value for a pixel or subpixel in the output video image from pixel or subpixel values in the input image lying in a range between a corresponding support point and a neighbouring support point;
wherein the method further comprises:
distributing the support points of two successive lines or columns of the input video image such that at least one range lying between two support points of one line or column of the input image spatially overlaps offset with respect to a corresponding range of a preceding or succeeding line or column of the input video image; and
controlling the display device to reproduce in the display area the selected or calculated pixel or subpixel value, corresponding to the output video image.
2. The method of claim 1 , further comprising the step of determining the values for neighbouring pixels in the output video image from the pixels between a corresponding support point and a neighbouring support point in the input image such that adjacent output pixels have a maximum difference.
3. The method as claimed in claim 1 , further comprising calculating a pixel or subpixel value for a pixel or subpixel in the output video image from pixel or subpixel values in the input video image lying between a corresponding support point and both neighbouring support points.
4. A control circuit for controlling a display device having a microprocessor, a program memory and a main memory, and also input means for scaling ratios, wherein the control circuit is adapted to execute the method of claim 1 .
5. A film scanner with a control monitor, further having a control circuit according to claim 4 .