Symptoms

FineReader Engine 12 recognizes a checkmark in an empty area of the image.

Cause

The light background is presented in the image.

Resolution

Despite the image looks empty, it may contain a light background which being considered black after the binarization. Here is the way to check the percentage of black:

int amountOfBlack = checkMarkBlock.AmountOfBlack;

If the percentage is higher than 0, there is a part of the image that is considered black. 

To resolve this, it is possible to indicate BinarizationThreshold during the image preparation.
This property is used for fine-tuning the brightness threshold during image preprocessing: the pixels with a brightness higher than the threshold will be replaced with white pixels, the rest with black.

The value of this property may be in the range of 0 to 255. The default value of this property is -1, which means that the binarization threshold is determined by FineReader Engine automatically.

The value of BinarizationThreshold may be defined according to needs, but usually, 15 will be ok.