Ngenuity TWAIN Data Source November 19, 2009
Page 98 of 99
5 IMPLEMENTATION NOTES
5.1
IMAGE CONTRAST BRIGHTNESS GAMMA
BBH recommends the following user controls implementation
RGB or GRAY Scanning (Color or Grayscale):
Image Brightness ICAP_BRIGHTNESS
Image Contrast ICAP_CONTRAST
Image Gamma BBH_CAP_CAM_GAMMA
BW (Bitonal) Scanning
Image Brightness ICAP_AUTOBRIGHT (defaultl to Auto-Brightness feature)
Image Contrast ICAP_CONTRAST
Image Gamma BBH_CAP_CAM_GAMMA
The following Camera parameters are set by the scanner manufacturer and are not considered to be
user set parameters and should not be exposed to a scanner user (unless for the most advanced
factory users):
BBH_CAP_CAM_BRIGHTNESS
BBH_CAP_CAM_CONTRAST
Therefore the TDS user is required to keep the default settings to FALSE for
BBH_CAP_CAM_BRIGHTNESS_ENABLE
BBH_CAP_CAM_CONTRAST_ENABLE
BBH recommend the use of BBH_CAP_CAM_GAMMA for camera gamma control as this
parameter works within the camera full depth of color palette (maximum bit depth) compared the
the ICAP_GAMMA that controls gamma in the Image Processing buffer RGB 24-bit more limited
color palette.
5.2 COLOR IMAGE IN BMP MODE
TWFF_BMP file type with ICAP_PIXELTYPE = RGB creates uncompressed file however the
scanner hardware actually uses JPEG compression with JPEGQUALITY = 99 and
JPEG_SUBSAMPLING = 444 for RESOLUTION at 400 DPI or less and 422 for RESOLUTION
higher than 400 DPI.
5.3 M
ULTISTREAM MODE
In Multistream mode, the scanner outputs multiple images per pages with up to 4 images for the
Front Page and 4 images for the Back Page. The multistream mode is quite versatile but also contains
some limitations explained below.
Duplex
• Front and Back Main Pages are required to have same Orientation, Page Size, Resolution, JPEG
Compression and Color Mode. (This is not a multistream mode specific requirement).
• Front and Back Sub-Windows settings are independents, except for JPEG compression.
Color Mode
• Sub-Windows Color mode need to be the same or derived from Main Page Color mode; Black
and White (BW) can be derived from Color or Grayscale.
• The combination of Color (Main Page) and Grayscale (Sub-windows) is not supported.
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