Down-scaling technique for bi-level images

Claim 1

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the step of: horizontally scaling said pixel pattern, said step of horizontally scaling said pixel pattern comprising the steps of: determining a horizontal scale factor for reducing a length of said horizontal rows of pixels; receiving an original group of bits corresponding to a group of pixels in a row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying bits to be deleted from said group of bits to achieve said horizontal scale factor; identifying which of said bits to be deleted meet a first criterion, said first criterion being that said bit to be deleted is of said first logic level bounded by bits of said second logic level, wherein bits immediately to either side of said group of bits along said row are presumed to be of said second logic level; setting a bit, within said group and adjacent to a bit to be deleted which met said first criterion, from said second logic level to said first logic level; deleting said bits to be deleted to reduce a size of said group of bits to achieve said horizontal scale factor; and outputting a horizontally scaled group of bits.

Claim 2

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the step of: horizontally scaling said pixel pattern, said step of horizontally scaling said pixel pattern comprising the steps of: determining a horizontal scale factor for reducing a length of said horizontal rows of pixels; receiving an original group of bits corresponding to a group of pixels in a row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying bits to be deleted from said group of bits to achieve said horizontal scale factor; identifying which of said bits to be deleted meet a first criterion, said first criterion being that said bit to be deleted is of said first logic level bounded by bits of said second logic level, wherein bits immediately to either side of said group of bits along said row are presumed to be of said second logic level; setting a bit, within said group and adjacent to a bit to be deleted which met said first criterion, from said second logic level to said first logic level; deleting said bits to be deleted to reduce a size of said group of bits to achieve said horizontal scale factor; and outputting a horizontally scaled group of bits.

Claim 14

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the steps of: vertically scaling said pixel pattern comprising the steps of: determining a vertical scale factor for reducing a vertical height of said columns of pixels; receiving a first row of bits corresponding to a first row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying that said first row of pixels is to be deleted from said pixel pattern to achieve said vertical scale factor; receiving groups of bits in a second row of bits corresponding to a second row of pixels which are not to be deleted; determining whether a group of pixels represented by a group of said bits in said second row of bits contains characteristics of text; for all bits in a group corresponding to a group of pixels determined to have said characteristics of text, logically OR'ing each bit in said group of bits with each corresponding bit in said first row of bits to form an altered second row of bits; deleting said first row of bits; and outputting said altered second row of bits.

Claim 15

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the steps of: vertically scaling said pixel pattern comprising the steps of: determining a vertical scale factor for reducing a vertical height of said columns of pixels; receiving a first row of bits corresponding to a first row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying that said first row of pixels is to be deleted from said pixel pattern to achieve said vertical scale factor; receiving groups of bits in a second row of bits corresponding to a second row of pixels which are not to be deleted; determining whether a group of pixels represented by a group of said bits in said second row of bits contains characteristics of text; for all bits in a group corresponding to a group of pixels determined to have said characteristics of text, logically OR'ing each bit in said group of bits with each corresponding bit in said first row of bits to form an altered second row of bits; deleting said first row of bits; and outputting said altered second row of bits.

Claim 22

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the steps of: vertically scaling said pixel pattern comprising the steps of: determining a vertical scale factor for reducing a vertical height of said columns of pixels; receiving groups of bits in a first row of bits corresponding to a first row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying that said first row of pixels is to be deleted from said pixels pattern to achieve said vertical scale factor; receiving groups of bits in a second row of bits corresponding to a second row of pixels which are not to be deleted; determining whether a group of bits is part of text or part of a picture comprising the steps of: detecting whether said group of bits meets a first criterion, said first criterion being that said group of bits has exactly one run of bits of said second logic level or exactly one run of bits of said first logic level, where a run of bits is defined as a group of consecutive bits of a same logic level bounded by bits of the other logic level, wherein bits immediately to either side of said group along said row are presumed to be of said first logic level; if said group of bits meets said first criterion, determining that said group of bits forms part of text; if it is determined that said group of bits is part of text, then logically OR'ing each bit in said first row of bits with each corresponding bit in said second row of bits to form an altered second row of bits; deleting said first row of bits; and outputting said altered second row of bits.

Claim 23

A method for down scaling an original pixel pattern having horizontal rows of pixels and vertical columns of pixels, said method comprising the steps of: vertically scaling said pixel pattern comprising the steps of: determining a vertical scale factor for reducing a vertical height of said columns of pixels; receiving groups of bits in a first row of bits corresponding to a first row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; identifying that said first row of pixels is to be deleted from said pixels pattern to achieve said vertical scale factor; receiving groups of bits in a second row of bits corresponding to a second row of pixels which are not to be deleted; determining whether a group of bits is part of text or part of a picture comprising the steps of: detecting whether said group of bits meets a first criterion, said first criterion being that said group of bits has exactly one run of bits of said second logic level or exactly one run of bits of said first logic level, where a run of bits is defined as a group of consecutive bits of a same logic level bounded by bits of the other logic level, wherein bits immediately to either side of said group along said row are presumed to be of said first logic level; if said group of bits meets said first criterion, determining that said group of bits forms part of text; if it is determined that said group of bits is part of text, then logically OR'ing each bit in said first row of bits with each corresponding bit in said second row of bits to form an altered second row of bits; deleting said first row of bits; and outputting said altered second row of bits.

Claim 25

A method for determining whether a group of bits is part of text or part of a picture, said method comprising the steps of: receiving groups of bits in a row of bits corresponding to a row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; for each group, detecting whether said group of bits meets a first criterion, said first criterion being that said group of bits has exactly one run of bits of said second logic level or exactly one run of bits of said first logic level, where a run of bits is defined as a group of consecutive bits of a same logic level bounded by bits of the other logic level, wherein bits immediately to either side of said group along said row are presumed to be of said first logic level; and if said group of bits meets said first criterion, determining that said group of bits forms part of text.

Claim 26

A method for determining whether a group of bits is part of text or part of a picture, said method comprising the steps of: receiving groups of bits in a row of bits corresponding to a row of pixels, a bit of a first logic level representing a dot to be displayed by a display device, a bit of a second logic level representing that a dot is not to be displayed; for each group, detecting whether said group of bits meets a first criterion, said first criterion being that said group of bits has exactly one run of bits of said second logic level or exactly one run of bits of said first logic level, where a run of bits is defined as a group of consecutive bits of a same logic level bounded by bits of the other logic level, wherein bits immediately to either side of said group along said row are presumed to be of said first logic level; and if said group of bits meets said first criterion, determining that said group of bits forms part of text.