User guide

Quantity One User Guide
12-30
Click on the Background Box button, then drag on the image, defining an area
that is representative of the background for your entire gel image. The
average intensity of the pixels within the box will be used as the background
level to be subtracted from your image.
Background Stripe
This function is useful when the image background is horizontally uniform
but changes from the top to the bottom of the image, such as on a gradient
gel.
To subtract a background gradient, click on Background Stripe, then drag on
a background region to create a lane-like box down the length of the image.
The average intensity of the pixels in every horizontal pixel row within the
stripe will be subtracted from that entire pixel row. This way, if your image
has more background at the bottom than at the top, more background will be
removed from the lower regions of the image.
Note: Make sure that your background stripe box stretches down the entire
length of the part of the image you are interested in. If your background
stripe is shorter than your image length, the software will take the last
background value at top end of the stripe and subtract it from the upper
part of the image, and take the last background value at the bottom of the
stripe and subtract it from the lower part of the image.
When you draw a stripe, the minimum and maximum intensities in the stripe
are displayed next to the Min and Max labels in the box. Also, the average
intensity value for the entire stripe is displayed next to Avg.
Completing the Subtraction
When you are happy with the background subtraction shown in the preview
image, click on the OK button at the bottom of the dialog box.
Because whole-image background subtraction is an irreversible process, a
pop-up box will give you the option of subtracting from the original image,
creating a copy of the image to subtract from, or cancelling out of this
operation.