Title:
THRESHOLD LEVEL DETERMINING DEVICE
Document Type and Number:
Japanese Patent JPS6481077
Kind Code:
A
Abstract:
PURPOSE:To determine an indistinct threshold level by deriving a second luminance for dividing the luminance of an image whose threshold level is determined, in the same ratio as a ratio in which a first luminance for binarizing a reference image divides a histogram of its luminance, and calculating both of them. CONSTITUTION:The luminance of each picture element of an image is stored in an image buffer 15a, and a luminance histogram is calculated and stored in a histogram buffer 15b. An image in which the maximum value of an accurate histogram is shown is set as a reference image and the luminance of its minimum value is set as a first threshold level Xtb. On the other hand, the first luminance Xrb for dividing a histogram frequency stored in said histogram buffer 15b, into one-to-one is calculated. Subsequently, the luminance for dividing an inputted image, as well to one-to-one in the same way is derived, and it is set as a second luminance Xr. Next, a difference DELTAXr between the first and the second luminances is calculated, prescribed weighting alpha, beta is performed to Xtb and DELTAXr and the second threshold level Xt(=alphaXtb+betaDELTAXr) is derived. In such a way, as for a new input image, by threshold level can be determined without using the minimum value.
Inventors:
AKAHA KOICHI
Application Number:
JP23845287A
Publication Date:
March 27, 1989
Filing Date:
September 22, 1987
Export Citation:
Assignee:
BROTHER IND LTD
International Classes:
G06T1/00; (IPC1-7): G06F15/62; G06F15/64