Facsimile and static presentation processing – Static presentation processing – Communication
Reexamination Certificate
1999-08-18
2003-02-11
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Communication
C358S001900, C358S002100
Reexamination Certificate
active
06519050
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a client/server system for measuring and displaying color density of documents (including images) located on remote file servers wherein access occurs over a local or wide area network such as the Internet based World Wide Web (WWW).
BACKGROUND OF THE INVENTION
A basic function of World Wide Web browsers in common use today, such as Netscape Navigator and Microsoft Internet Explorer, is to allow web pages stored on a remote Web server to be retrieved and viewed. The user initiates a viewing session on a web browser by specifying a particular URL corresponding to a page to be viewed. The web server transmits the various elements of the requested page to the browsing application. Any special data formats, e.g., video, audio, certain images, documents not written in HTML language, etc., are treated by one or more web browser software plug-ins on the client computer.
A common need is to be able to view digital images on the client computer and be able to read, display and record color density measurements over wide area networks or the Internet. The digital images are stored on image servers located somewhere in the network and are not stored on the user's local computer. In addition, it would be useful if the system were able to aid the user in interpreting the color measurement readings to match a specific printing system with a particular color book. Note that the users of the system may be located anywhere in the world as long they have a connection to the wide area network, e.g., the Internet.
In the printing and graphic arts industry, printed color is measured utilizing tools known as densitometers. Color is measured for many reasons, a major reason being tocalibrate printers used in the printing process so that the printed color can be matched to an original item or a known standard. When the printed data is still in digital form it is common practice in the printing and graphic arts fields to measure color values in the digital image by means of software that functions to emulate the physical device for measuring color, the software being typically provided with the image editing and display systems.
This electronic densitometer allows the gray level of each of the color components to be measured at a specific coordinate location in the image. The measured color values may be expressed in the form of component color values, e.g., cyan (C), magenta (M), yellow (Y) and black (K), for each color component, i.e., separation, present in the measured color image. Alternatively, the measured color values may be expressed as composite color space vectors that represent the color space coordinates of the measured color at a location being measured. The color space vectors are color space coordinates within a system-independent coordinate system such as CIE XYZ or L*, a*, b*.
Spot colors, i.e., special colors, such as gold, silver or those used in color systems like Pantone® or Toyo may also be represented. Since the computer based video display systems represent the image using the RGB color space, it is far more preferable to measure color using the original color channels from the digital image file. This ensures that the correct values are presented to the user, i.e., before they are converted to RGB.
A problem arises, however, when a digital image is subject to color space transformations such as a conversion from the CMYK color space to CIELab or RGB. When conversions are used, it is highly likely that the resulting densitometer readings are not the same as they would be using the original color data. This is due to the fact that the color values are rounded during the conversion calculations introducing errors and that the transformations themselves are not reversible.
The problem is further compounded when the images are compressed before being transmitted to the client workstation over a network such as a WAN or the Internet. In this case, it is difficult to measure color on images that are compressed because the color space of the images typically changes as part of the compression algorithm. Thus, color information cannot be reliably or accurately measured at the client site receiving the compressed images.
In addition, a problem with current systems is that the color viewed on the screen is not sufficient to provide accurate density data on the underlying image. The ability to measure color of an image displayed on screen is very useful when working with an image that is ultimately to be printed. In the pre-press phase of generating printed images, it is very helpful to be able to measure the spot color of an image in any desired location. This information is used in conjunction with a color book to view the actual colors that will be printed when the image goes to press.
In currently available imaging systems, however, color density readings are made directly from an off-screen memory that is located within the user workstation where the image is viewed. Thus, the off-screen memory in the user image workstation holds the entire original image that may be 10, 50, 100 MB or more. Alternatively, the original images are located on a file system wherein both the file system and the image workstation are connected to a high speed local area network. In the case where off-screen memory is used to store the original image, color readings are made directly from the off-screen memory where the image is stored. In the case where a file system connected to a LAN is used to store the image, color readings are made directly from the image file server.
An example of a commercially available product is widely used Adobe Photoshop® application program. This software program incorporates a digital color densitometer feature that functions to read color values at a specific coordinate of the image. This tool, however, reads the pixel color value information from off screen memory that holds a copy of the original image.
In another example, the Scitex Prismax retouching workstation is an image processing workstation designed for the graphic arts industry. The workstation incorporates a digital color densitometer that functions to read and display color component values at a specific image coordinate. Unlike Adobe Photoshop, however, this system samples the original image that resides on an image file server connected to a LAN.
A disadvantage of the prior art densitometer systems is that they are not suitable for use with large images where the user image workstation and the original image are either not co-located in the same device or are not connected by a high speed LAN. In particular, the prior art systems are not practical for use with user image workstations that are connected to image file servers over low rate connections such 28.8, 33.6 or 56 Kbps dial up access over the Internet.
In addition, the prior art systems are not client/server solutions whereby multiple users can simultaneously access the same image. Further, these systems do not permit users to work directly with printing press references such as reference color books. Some prior art systems compress the image in memory so that the image takes up less memory to store or the image is decompressed with the result that the decompressed image is not the same as the original. In this case, color densitometer readings are not from the original image but from some altered version of the original image.
For example, in prior art systems color density measurements are taken from a local frame buffer containing color data in RGB color space. The color data is converted into CMYK values using one of several well-known conversion techniques for converting color from the RGB color space to CMYK. This process, however, is not accurate due to the conversion between color spaces that is required.
In addition, it would be desirable to record densitometer readings as annotations on the image itself for use by others. More than one densitometer reading should be able to be displayed over the image. Others viewing the document would then be able to view the densitomete
Dementiev Roman
Eintracht Zvika
Grant II Jerome
RTImage Ltd.
Zarretsky Howard
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