COLOR cameras only.
The White Shading feature provides control over the individual red, green and blue channel gains so that non-standard color balance can be achieved. One-push Auto will attempt to white balance the gains (match the histogram peaks of the brightest area in each color channel) based on the image data in the current ROI.
|
|
|
Note |
The auto white shading algorithm is based on a brightfield microscopy where the background is bright and white. The algorithm balances the brightest areas of the image to white. When used in reflected light microscopy or in colored environments, the brightest areas in the image must be neutral in color. If not, it is best to perform the auto white shading using a grey card. |
White shading is performed prior to other image processing steps and is independent of the white balance (color correction) settings.
Setting a gain parameter to zero will effectively turn off that color channel – it will output a zero value.
|
|
|
Note |
Setting a color channel gain to zero and also setting the saturation feature to zero will result in values on that color channel. The color channel gains affect the raw sensor data and any image processing performed on-board the camera, like the saturation adjustment, may modify the values on the color channels. |
PxLGetFeature, PxLSetFeature
|
Feature |
Number of Parms |
Parameters |
Units |
Restrictions |
|
FEATURE_WHITE_SHADING Camera color channel gains |
3 |
fRedGain |
Decibels (dB) |
N/A |
|
fGreenGain |
Decibels (dB) |
N/A | ||
|
fBlueGain |
Decibels (dB) |
N/A |
|
Camera |
Presence |
Read Only |
Auto |
Manual |
One-time Auto |
Off |
CiD |
|
All Cameras |
Yes |
No |
No |
Yes |
Yes |
No |
Yes |
|
Camera |
Parameter |
Unit |
Type |
Min |
Max |
Default |
Step Size |
Comments |
|
742, 681C |
Gain Red |
None |
Absolute |
0 |
4 |
1.06 |
0.0156 |
|
|
Gain Green |
None |
Absolute |
0 |
4 |
1.0 |
0.0156 |
| |
|
Gain Blue |
None |
Absolute |
0 |
4 |
1.57 |
0.0156 |
| |
|
762 |
Gain Red |
None |
Absolute |
0 |
4 |
1.0 |
0.01 |
|
|
Gain Green |
None |
Absolute |
0 |
4 |
1.0 |
0.01 |
| |
|
Gain Blue |
None |
Absolute |
0 |
4 |
2.0 |
0.01 |
| |
|
774, 776, 778, 622C, 623C, 625C |
Gain Red |
None |
Absolute |
0 |
4 |
1.0 |
0.0156 |
|
|
Gain Green |
None |
Absolute |
0 |
4 |
1.0 |
0.0156 |
| |
|
Gain Blue |
None |
Absolute |
0 |
4 |
1.73 |
0.0156 |
| |
|
782, 686C |
Gain Red |
None |
Absolute |
0 |
4 |
1.42 |
0.0156 |
|
|
Gain Green |
None |
Absolute |
0 |
4 |
1.0 |
0.0156 |
| |
|
Gain Blue |
None |
Absolute |
0 |
4 |
1.08 |
0.0156 |
| |
|
870C, 950 |
Gain Red |
None |
Absolute |
0 |
8 |
1.0 |
0.0312 |
|
|
Gain Green |
None |
Absolute |
0 |
8 |
1.0 |
0.0312 |
| |
|
Gain Blue |
None |
Absolute |
0 |
8 |
2.0 |
0.0312 |
|
The white shading control, as described in the IIDC 1.31 specification, only provides for 8 bits of shading data per channel. Additional CSRs are provided to allow 32-bit resolution in color channels. The White Shading can also be set by the Auto mode of the White Balance feature.
|
Cameras |
Feature |
Feature Control Register Values |
Corresponding Absolute Values |
||
|
Min |
Max |
Min |
Max | ||
|
600 & 700 |
White Shading |
0 |
255 |
0.0 |
4.0 |
|
800 & 900 |
0 |
255 |
0.0 |
8.0 | |
The IIDC 1.31 specification defines White Shading as controlling three values, the red, green and blue channel compensations, but only one absolute value register is defined for White Shading. This does not allow for control of the separate channel compensations with standard engineering units. So extra absolute value registers are defined as follows.
The offsets for the White_Shading absolute value CSRs are defined in the ABS_CSR_HI_INQ_14 register (offset 738h). This will define the offsets for the red channel compensation CSRs. The absolute value CSR offsets for the green and blue channels can be calculated as follows : quadlet offset of green or blue CSRs = ABS_CSR_HI_INQ_14 + 3 * X (where X = 1 for green and X = 2 for blue).
