Patent ID: 6134346
Filing Date: 2000-10-17
Classification: H04N

Abstract:
A method for extracting a selected subject from an image, including those portions of the subject that are semitransparent, by removing all elements of the background surrounding the subject, and also removing those background elements visible through semitransparent areas of the subject, where said method comprises the steps of;a) drawing, on a display of said image, an inner boundary line on the subject near to an edge of said subject,b) drawing an outer boundary line on said display, on the background near to the subject, but spaced at a distance sufficient to avoid inclusion of any element of said subject,c) generating a Clear Frame by filling the area inside said outer boundary line with RGB levels generated by interpolation and/or extrapolation of the RGB levels existing on and/or outside said outer boundary line,d) generating an Expanded Subject Frame by replacing the RGB levels in the area bounded by said inner and outer boundary lines with RGB levels generated by extrapolation of the RGB levels existing on and/or inside said inner boundary line,e) calculating an estimated Percent Background RGB Contribution (Matte Signal) to each pixel in the bounded area using equation:percentage background contribution=(F(pixRGB)-F(subRGB)) / (F(bgRGB)-F(subRGB)),where: F is any linear function of the form, F(RGB)=k.sub.1 R+k.sub.2 G+k.sub.3 B,pixRGB is observed RGB at a pixel at a given address in the bounded area,subRGB is RGB obtained from the Expanded Subject Frame at said given address,bgRGB is RGB obtained from the Clear Frame at said given address,f) generating a Matte Frame by assigning a matte value of 1.0 to all pixels outside said outer boundary line, and assigning a matte value of 0.0 to all pixels inside said inner boundary line, and including the bounded area matte signal of step `e` to complete the full Matte Frame signal,g) multiplying RGB levels at each pixel in the Clear Frame by the matte signal at the corresponding pixel in the Matte Frame to form their product,h) subtracting said product from the RGB levels of the original image to result in a Processed Foreground image of the subject, where said subject appears to have been photographed against a black backing, with no residual elements of the background remaining in the background nor in semitransparent areas of the subject.