text_line_orientation — Determines the orientation of a text line or paragraph.
text_line_orientation determines the orientation of a single text line or a paragraph in relation to the horizontal image axis. If the orientation of a single text line should be determined, the range for the OrientationFrom and OrientationTo should be in the interval from -pi/4 to pi/4.
The parameter Region specifies the area of the image in which the text lines are located. The Region is only used to reduce the working area. To determine the slant, the gray values inside that area are used. The text lines are segmented by the operator text_line_orientation itself. If more than one region is passed, the numerical values of the orientation angle are stored in a tuple, the position of a value in the tuple corresponding to the position of the region in the input tuple.
CharHeight specifies the approximately height of the existing text lines in the region Region. It´s assumed, that the text lines are darker than the background.
The search area can be restricted by the parameters OrientationFrom and OrientationTo, whereby also the runtime of the operator is influenced.
With the calculated angle OrientationAngle and operators like affine_trans_image, the region Region of the image Image can be rotated such, that the text lines lie horizontally in the image. This may simplify the character segmentation for OCR applications.
Area of text lines.
Height of the text lines.
Default value: 25
Typical range of values: 1 ≤ CharHeight
Restriction: CharHeight >= 1
Minimum rotation of the text lines.
Default value: -0.523599
Typical range of values: -3.141593 ≤ OrientationFrom ≤ 3.141593
Restriction: -2 * pi <= OrientationFrom <= 2 * pi
Maximum rotation of the text lines.
Default value: 0.523599
Typical range of values: -3.141593 ≤ OrientationTo ≤ 3.141593
Restriction: OrientationFrom <= OrientationTo && OrientationTo < OrientationFrom + pi
Calculated rotation angle of the text lines.
read_image(Image,'letters') text_line_orientation(Image,Image,50,rad(-80),rad(80),OrientationAngle) rotate_image(Image,ImageRotate,-OrientationAngle/rad(180)*180,'constant')
If the input parameters are set correctly, the operator text_line_orientation returns the value 2 (H_MSG_TRUE). Otherwise an exception will be raised.
rotate_image, affine_trans_image, affine_trans_image_size