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Pseudo-tag Encoding of Digital Image Information

IP.com Disclosure Number: IPCOM000130698D
Publication Date: 2005-Nov-01
Document File: 3 page(s) / 30K

Publishing Venue

The IP.com Prior Art Database

Abstract

In processing digital images, it is common to use tags or hints that give the image processor information about the image that it uses to decide the type or degree of processing to be applied. The tags are provided along with the image, sometimes interleaved with the image data and sometimes as a separate record. This can result in increased data to be transmitted and often requires an agreed upon data structure that can be honored by software applications receiving the data. This invention provides a means of encoding information about the image into pseudo-tags in the image itself. This provides a mechanism for communicating information about the image without adding bandwidth and also makes the pseudo-tag information invisible to receiving applications.

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Pseudo-tag Encoding of Digital Image Information

In processing digital images, it is common to use tags or hints that give the image processor information about the image that it uses to decide the type or degree of processing to be applied.  The tags are provided along with the image, sometimes interleaved with the image data and sometimes as a separate record.  This can result in increased data to be transmitted and often requires an agreed upon data structure that can be honored by software applications receiving the data.

This invention provides a means of encoding information about the image into pseudo-tags in the image itself.  This provides a mechanism for communicating information about the image without adding bandwidth and also makes the pseudo-tag information invisible to receiving applications.  A specific example is given for encoding neutral and text tags into the chrominance channel.

In processing color digital images, it is sometimes desirable to force near-neutral colors to be precisely neutral.  Several methods have been described for detecting such near-neutral pixels1.  In a cylindrical color space like L*a*b* for example, pixels with sufficiently small a* and b* may be adjusted to a*=b*=0.  In such cases, there will be values of a* and b* that are unused since they are re-set to identically zero for pixels identified as neutral.  In effect, the combination of a*=b*=0 acts as a tag for neutral pixels.  This invention codes the unused values to carry information about other pixel characteristics.

For neutral pixels, it is sometimes useful to classify them as being edge pixels, particularly when processing black text separately from color or pictorial data.  This invention codes edge information into the unused values of pixels that have been re-mapped into purely neutral colors.  Consider a simple case where a* and b* are set to zero whenever a*<2 and b*<2.  The values a*=1 or b*=1 will not occur anywhere in the image.  When neutral pixels are also found to be edge pixels, the code a*=1 can be used to represent the edge tag, actually a pseudo-tag.  Similarly, b*=1 could be used to carry some other information about a neutral pixel, for example a background tag.

The advantage of this type of pseudo-tag is that it resides within the image itself so it doesn’t require any special handling.  The image can be transferred like any other image.  In fact, it is not required that the image path even know that the pseudo-tags have been added.  For applications that do know, however, special image processing can be used to take advantage of the additional information encoded in the tags.

In the case where the image path treats the image as a raw scanned image, there will be a slight shift in the average density of neutral pixels because of the encoding.  Note, however, that there will already have been such a shift due to the truncation that occurs when the pixels where forced...