text_line_orientationtext_line_orientationTextLineOrientationtext_line_orientationTextLineOrientationTextLineOrientation (Operator)

Name

text_line_orientationtext_line_orientationTextLineOrientationtext_line_orientationTextLineOrientationTextLineOrientation — Determines the orientation of a text line or paragraph.

Signature

text_line_orientation(Region, Image : : CharHeight, OrientationFrom, OrientationTo : OrientationAngle)

text_line_orientationtext_line_orientationTextLineOrientationtext_line_orientationTextLineOrientationTextLineOrientation 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 OrientationFromOrientationFromOrientationFromOrientationFromOrientationFromorientationFrom and OrientationToOrientationToOrientationToOrientationToOrientationToorientationTo should be in the interval from -pi/4 to pi/4.

The parameter RegionRegionRegionRegionRegionregion specifies the area of the image in which the text lines are located. The RegionRegionRegionRegionRegionregion 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_orientationtext_line_orientationTextLineOrientationtext_line_orientationTextLineOrientationTextLineOrientation 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.

CharHeightCharHeightCharHeightCharHeightCharHeightcharHeight specifies the approximately height of the existing text lines in the region RegionRegionRegionRegionRegionregion. It's assumed, that the text lines are darker than the background.

The search area can be restricted by the parameters OrientationFromOrientationFromOrientationFromOrientationFromOrientationFromorientationFrom and OrientationToOrientationToOrientationToOrientationToOrientationToorientationTo, whereby also the runtime of the operator is influenced.

With the calculated angle OrientationAngleOrientationAngleOrientationAngleOrientationAngleOrientationAngleorientationAngle and operators like affine_trans_imageaffine_trans_imageAffineTransImageaffine_trans_imageAffineTransImageAffineTransImage, the region RegionRegionRegionRegionRegionregion of the image ImageImageImageImageImageimage can be rotated such, that the text lines lie horizontally in the image. This may simplify the character segmentation for OCR applications.

Parallelization

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.

Parameters

RegionRegionRegionRegionRegionregion (input_object) region(-array) → object

Area of text lines.

ImageImageImageImageImageimage (input_object) singlechannelimage → object (byte / uint2)

Input image.

CharHeightCharHeightCharHeightCharHeightCharHeightcharHeight (input_control) integer → (integer)

Height of the text lines.

Default value: 25

Typical range of values: 1 ≤ CharHeight CharHeight CharHeight CharHeight CharHeight charHeight

Restriction: CharHeight >= 1

OrientationFromOrientationFromOrientationFromOrientationFromOrientationFromorientationFrom (input_control) angle.rad → (real)

Minimum rotation of the text lines.

Default value: -0.523599

Typical range of values: -3.141593 ≤ OrientationFrom OrientationFrom OrientationFrom OrientationFrom OrientationFrom orientationFrom ≤ 3.141593

Restriction: -2 * pi <= OrientationFrom <= 2 * pi

OrientationToOrientationToOrientationToOrientationToOrientationToorientationTo (input_control) angle.rad → (real)

Maximum rotation of the text lines.

Default value: 0.523599

Typical range of values: -3.141593 ≤ OrientationTo OrientationTo OrientationTo OrientationTo OrientationTo orientationTo ≤ 3.141593

Restriction: OrientationFrom <= OrientationTo && OrientationTo < OrientationFrom + pi

OrientationAngleOrientationAngleOrientationAngleOrientationAngleOrientationAngleorientationAngle (output_control) angle.rad(-array) → (real)

Calculated rotation angle of the text lines.

Example (HDevelop)

read_image(Image,'letters')
text_line_orientation(Image,Image,50,rad(-80),rad(80),OrientationAngle)
rotate_image(Image,ImageRotate,-OrientationAngle/rad(180)*180,'constant')

Result

If the input parameters are set correctly, the operator text_line_orientationtext_line_orientationTextLineOrientationtext_line_orientationTextLineOrientationTextLineOrientation returns the value 2 (H_MSG_TRUE). Otherwise an exception will be raised.

Possible Successors

rotate_imagerotate_imageRotateImagerotate_imageRotateImageRotateImage, affine_trans_imageaffine_trans_imageAffineTransImageaffine_trans_imageAffineTransImageAffineTransImage, affine_trans_image_sizeaffine_trans_image_sizeAffineTransImageSizeaffine_trans_image_sizeAffineTransImageSizeAffineTransImageSize

Module

Foundation

Operators