System for determining the size of an original image, such as in a digital copier
View Patent ↗An input scanner, such as used in a digital copier, accepts original documents on sheets of any number of possible sizes within a single job. The video output of the scanner is applied to an algorithm to determine the length, along a process direction, of useful image data on each sheet. From such a determination, a size of output copy sheets can be automatically selected, or the image can be automatically changed in size in subsequent processing. A prescan of the original documents is not required.
1. A method of determining a size of an image associated with a set of digital image data, the image data comprising a plurality of scanlines, each scanline comprising a plurality of pixels, each pixel having a luminance associated therewith, the method comprising:
scanning an original image on a sheet, thereby obtaining a set of image data comprising a plurality of scanlines, each scanline comprising a plurality of pixels;
for each pixel of a plurality of pixels in a scanline, incrementing a pixel difference counter if a luminance difference of the pixel relative to a second pixel in the scanline exceeds a predetermined luminance difference threshold;
for each pixel of a plurality of pixels in a scanline, incrementing a line difference counter if a luminance difference of the pixel relative to a corresponding pixel in a corresponding position in a second scanline exceeds a predetermined luminance difference threshold;
for each scanline, updating a scanline number register if the pixel difference counter is within a predetermined pixel difference counter range or the line difference counter is within a predetermined line difference counter range;
determining a dimension of the original image based on a value of the scanline number register; and
printing an image derived from the original image, using a determined dimension of the original image.
2. The method of claim 1 , further comprising
for each of a plurality of scanlines, not updating the scanline number register if a plurality of pixels in the scanline are in a predetermined range of luminance consistent with a backing.
3. The method of claim 2 , further comprising
using chroma values for the plurality of scanlines to determine if the plurality of pixels in the scanline in a predetermined range of luminance consistent with a backing.
4. The method of claim 1 , wherein each pixel has a chroma value associated therewith and the method further comprising:
for a pixel in a scanline, determining if the chroma value of the pixel is within a predetermined range.
5. The method of claim 1 , wherein each pixel has a chroma value associated therewith and the method further comprising
for each pixel of a plurality of pixels in a scanline, incrementing a chroma counter if the chroma value of the pixel is not within a predetermined chroma range.
6. The method of claim 5 , wherein the predetermined chroma range is related to a color of a backing used in recording the digital image data from an original image.
7. The method of claim 1 , further comprising
for each scanline, updating the scanline number register if the chroma counter is within a predetermined chroma counter range.