Bayer Color Filter Alignment; Pixel Data Formats Available On Cameras With A Bayer Filter - Basler ace acA640-90gm User Manual

Color Creation and Enhancement
8.1.1

Bayer Color Filter Alignment

On all color camera modes that have senors equipped with a Bayer filter, the alignment of the filter
to the pixels in the acquired images is Bayer BG. Bayer BG alignment means that pixel one and
pixel two of the first line in each image transmitted will be blue and green respectively. And for the
second line transmitted, pixel one and pixel two will be green and red respectively. Since the pattern
of the Bayer filter is fixed, you can use this information to determine the color of all of the other pixels
in the image.
The Pixel Color Filter parameter indicates the current alignment of the camera's Bayer filter to the
pixels in the images captured by a color camera. You can tell how the current AOI is aligned to the
Bayer filter by reading the value of the Pixel Color Filter parameter.
Because the size and position of the area of interest on color cameras with a Bayer filter must be
adjusted in increments of 2, the color filter alignment will remain as Bayer BG regardless of the
camera's area of interest (AOI) settings.
For more information about the camera's AOI feature, see Section 10.5 on
8.1.2 Pixel Data Formats Available on Cameras with
a Bayer Filter
Bayer Formats
Cameras equipped with a Bayer pattern color filter can output pixel data in the Bayer BG 8, the
Bayer BG 12, or the Bayer BG 12 Packed pixel data format. When a color camera is set for one of
these three pixel data output formats, the pixel data is not processed or interpolated in any way. For
each pixel covered with a red portion of the filter, you get 8 or 12 bits of red data. For each pixel
covered with a green portion of the filter, you get 8 or 12 bits of green data. And for each pixel
covered with a blue portion of the filter, you get 8 or 12 bits of blue data. (This type of pixel data is
sometimes referred to as "raw" output.)
For complete details of these three pixel data output formats, see Section 9.1 on
Section 9.3 on page 171.
YUV Formats
All color cameras with a Bayer filter can output pixel data in YUV 4:2:2 Packed format or in YUV
4:2:2 (YUYV) Packed format.
When a color camera is set for either of these formats, each pixel in the captured image goes
through a two step conversion process as it exits the sensor and passes through the camera's
electronics. This process yields Y, U, and V color information for each pixel.
In the first step of the process, a demosaicing algorithm is performed to get RGB data for each pixel.
This is required because color cameras with a Bayer filter on the sensor gather only one color of
light for each individual pixel.
140
page 199.
page 163 and
Basler ace GigE