Image analysis – Color image processing
Patent
1996-07-01
2000-02-15
Au, Amelia
Image analysis
Color image processing
348649, G06K 900
Patent
active
06026179&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital video processing.
2. Description of the Related Art
In U.S. Pat. No. 5,450,500 and UK Patent Application 9407155.2 there is disclosed a digital colour processor (DCP) for colour correction in which only pixels that are specifically selected to be modified are processed by the digital circuitry. The pixels that are not to be modified are passed through the DCP without any processing that could create rounding or other errors. The processor comprises: pixels in a video picture; said data for modification if and only if it meets predetermined selection criteria; predetermined modification parameters to generate modified data; means with unmodified data from said input means to generate output data; and picture would be processed through the same signal modification path, possibly being converted from red, green and blue (RGB) to hue, saturation and luminance (HSL), and then back again to RGB, causing errors.
An advantage of the above system is that pixels to be modified can be selected not just in accordance with colour parameters but in accordance with other parameters such as position. Thus, only pixels within a certain area might be modified.
Pixel selection advantageously is carried out by using the architecture referred to below as the "pixel identification table" or alternatively as the "cache tag RAM". The pixel identification table stores digital bits which define which pixels will be selected from the pixel stream for modification. Pixels may be selected as a function of their color (hue) as in prior systems, and/or as a function of other criteria, such as saturation, luminance, (X,Y) pixel coordinates, sharpness, and texture, alone or in any combination.
Further, after a pixel or region to be changed has been isolated, other parameters besides (H,S,L) color attributes can be changed. For example, the sharpness or even the (X,Y) coordinates of a region can be changed. Modifying the (x,y) coordinates of a region would be useful, for example, for special effects such as moving an object in the picture. Detecting pixels according to their (X,Y) coordinates could also be useful for copying pixels at a given x,y from one frame to another for scratch concealment. The latter process might be carried out simply by, for the given X,Y, controlling the frame store of the DCP (discussed below), so that those specific pixels are not overwritten from frame to frame.
SUMMARY OF THE INVENTION
It has now been determined that it is possible to use such a system for more advanced handling of objects. Thus, it is possible to identify an object and to track it as it moves from frame to frame. It is also possible to store information relating to the object so that manipulations other than colour correction can be carried out.
According to one inventive aspect disclosed herein there is provided a method of digitally processing a sequence of video frames wherein an object which appears in the frames and undergoes relative motion or transformation is selected in a first frame by an operator; the pixels relating to the object are tagged in that frame by means of information including at least one colour or appearance attribute; corresponding pixels relating to the object are located automatically in subsequent frames, by means of said information including at least one colour or appearance attribute and by means of information indicating the expected position or shape of the object in the subsequent frames; and the pixels relating to the object in each of the frames are processed.
An appearance attribute could include texture or sharpness. A transformation could be in the form of morphing or the like or could be simply rotation.
Processing of the pixels could consist of colour correction, or could consist of storing information about the object so that it could be copied to another sequence, or modified in size, or replaced by a different object.
The information indicating the expected position of the object in each frame could
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Ahmed Samir
Au Amelia
Pandora International Ltd.
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