WINDOWS 1002000 PROFESSIONAL RESOURCE KIT [Electronic resources] نسخه متنی

Scanner and Camera Concepts

Scanners and cameras use a number of technologies to capture high-quality images, which are then transferred to your computer for editing and use. These technologies include the still imaging architecture, TWAIN, and ICM 2.0.

Still Imaging

Windows 2000 supports still image devices, such as scanners and cameras, by using a set of components that make up the still imaging architecture. Figure 15.6 is a graphical representation of the Windows 2000 still imaging architecture.

Figure 15.6 Still Imaging Architecture

The still imaging architecture is made up of the following components:

The application layer appears at the top of the imaging architecture. Users interact directly with the application to initiate image acquisition and manipulate images.

TWAIN or another application programming interface (API), which acquires images from a device such as a scanner or camera.

Still scanners and cameras that support ICM 2.0 accurately, which capture still image colors, enabling accurate color information for pictures.

Scanners and Cameras in Control Panel, which lets you add or remove scanners and cameras, configure ports and baud rates, and add, remove, or and select color profiles.

The still image event monitor, which waits for device events, such as a user pushing the button on a scanner. When the still image event monitor detects such an event, it launches the default application associated with handling image data.

The still image device driver interface (DDI), which communicates with devices to send commands. The DDI provides support of SCSI, parallel, serial, infrared, and USB devices. Support for Institute of Electrical and Electronics Engineers (IEEE) 1394 is incorporated using the Win32 Driver Model (WDM). Support for multifunction peripheral (MFP) devices is incorporated into the IEEE 1284.4 (DOT4) driver. For more information, see "Printing" in this book.

User mode minidrivers are supplied by device manufacturers to implement specific DDI functionality in the manufacturer's particular hardware. User mode minidrivers inform the DDI about the specific devices capabilities, such as test or status.

WDM still image drivers. These drivers use the win32 Driver Model to enable delivery on USB or SCSI buses. Devices that use COM ports do not require WDM drivers. For more information, see "Hardware Management" in this book.

TWAIN is an API. It facilitates seamless communication between imaging devices and software, without requiring that each image device and software combination have a different driver or API implementation. Each scanner or camera has one TWAIN driver that can be used by any application designed to manipulate images. Each layer of the TWAIN architecture works with adjacent layers to pass image data from an input device, such as a camera or scanner, to an application, such as Picture It! Windows 2000 includes version 1.6.1.3 of the TWAIN source manager. The TWAIN source manager lists possible sources of imaging data, such as specific types of scanners or cameras.

TWAIN Architectural Layers

TWAIN is comprised of a number of architectural layers, each of which serve a different function in transferring an image from a scanner or camera to an application. The TWAIN layers are as follows:

Application layer: An application such as Microsoft Picture It!, which is used to acquire an image from a TWAIN-compliant input device, such as a scanner or digital camera. The application requesting an image sends the request to the TWAIN data source.

TWAIN data source: A software component written by a hardware vendor to translate between TWAIN commands and device driver commands. Depending on the application, the data source may present a dialog for the user to select settings on the hardware device.

Device driver: The driver issues commands it receives from the TWAIN data source to the hardware to acquire an image and to check the status of the device.

Still image device: The physical input device, such as a scanner or digital camera.

If a user takes a photograph by using a digital camera and then loads that image onto their computer, the image should look the same on the monitor as it did when it was captured. When this same image is sent to a printer, the printed image should accurately reproduce the appearance of the colors seen by the camera and produced by the monitor.

Because different brands of monitors or printers present colors differently, it can be very difficult to produce images with accurate colors. ICM 2.0 ensures quality results by storing standard, objective color characteristics for each output device.

ICM 2.0 is an application programming interface (API) that conveniently ties together diverse technologies including scanning, capturing, displaying, and printing color pictures to yield consistent, high-quality color images without the user intervention required in the past. Color management solutions software works with profiles. Profiles are data about each device's representation of color. These profiles provide the operative information that enables the color management software to prepare an accurate color reproduction.

ICM supports international and industry standards, ensuring cross-platform compatibility. Image Color Management is based on the industry standard ICC profile, standardized Color Management Module (CMM), and the default sRGB color space (IEC 61966-2-1: 1999). Although this flexible system allows the use of any CMM, ICM uses LinoColor CMM by default. This makes Windows applications that use ICM 2.0 compatible with other platforms with respect to color management.

ICM provides ease-of-use for applications. For users who don't need to make advanced configuration choices, ICM 2.0 on Windows 2000 is set up to run transparently for printing. For users wanting to ensure color consistency with different devices and platforms, ICM provides full manual control with easy-to-use selection of alternative color profiles.

ICM has a modular, extensible architecture. Applications have the ability to support two levels of API—one that deals only in RGB, and one that works in multiple color spaces. As developers take advantage of these enhanced capabilities, advanced users are able to manage custom device profiles, work with CMYK, and select an alternate CMM for their color transformations.

ICM supports standard RGB (sRGB). Standard RGB (sRGB) complements current color management strategies by enabling a default method of handling color in the operating system and on the Internet. It efficiently provides good quality color representation and backward compatibility. Based on a calibrated colorimetric RGB color space, which is well-suited to monitors, television, scanners, digital cameras and printing systems, sRGB can be supported with minimum cost to software and hardware vendors.

Standard RGB is an international standard (IEC 61966-2-1: 1999), and is the default color space in Windows HTML, Cascading Style Sheets (CSS), .exif files which are produced by most digital cameras, and .png files. It is freely available to any software or hardware vendor. For more information about IEC 61966-2-1: 1999, see the International Electrotechnical Commission (IEC) link on the Web Resources page at http://windows.microsoft.com/windows2000/reskit/.

Standard RGB is the default color space in Windows 2000 for all color images that do not have another embedded profile or are not specifically tagged with other color information.

Table 15.2 highlights how ICM uses sRGB to handle colors when the application being used supports ICM 2.0. For example, the source might be a scanner or camera, and the destination might be a monitor or printer.

Table 15.2 Comparison of Color Profile Outcomes