text_line_orientationtext_line_orientationTextLineOrientationTextLineOrientationtext_line_orientation (Operator)

Name

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

Signature

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

Description

text_line_orientationtext_line_orientationTextLineOrientationTextLineOrientationTextLineOrientationtext_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 OrientationFromOrientationFromOrientationFromOrientationFromorientationFromorientation_from and OrientationToOrientationToOrientationToOrientationToorientationToorientation_to 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_orientationTextLineOrientationTextLineOrientationTextLineOrientationtext_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.

CharHeightCharHeightCharHeightCharHeightcharHeightchar_height 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 OrientationFromOrientationFromOrientationFromOrientationFromorientationFromorientation_from and OrientationToOrientationToOrientationToOrientationToorientationToorientation_to, whereby also the runtime of the operator is influenced.

With the calculated angle OrientationAngleOrientationAngleOrientationAngleOrientationAngleorientationAngleorientation_angle and operators like affine_trans_imageaffine_trans_imageAffineTransImageAffineTransImageAffineTransImageaffine_trans_image, 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.

Execution Information

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.

CharHeightCharHeightCharHeightCharHeightcharHeightchar_height (input_control) integer → (integer)

Height of the text lines.

Default value: 25

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

Restriction: CharHeight >= 1

OrientationFromOrientationFromOrientationFromOrientationFromorientationFromorientation_from (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 orientation_from ≤ 3.141593

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

OrientationToOrientationToOrientationToOrientationToorientationToorientation_to (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 orientation_to ≤ 3.141593

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

OrientationAngleOrientationAngleOrientationAngleOrientationAngleorientationAngleorientation_angle (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_orientationTextLineOrientationTextLineOrientationTextLineOrientationtext_line_orientation returns the value 2 (H_MSG_TRUE). Otherwise an exception will be raised.

Possible Successors

rotate_imagerotate_imageRotateImageRotateImageRotateImagerotate_image, affine_trans_imageaffine_trans_imageAffineTransImageAffineTransImageAffineTransImageaffine_trans_image, affine_trans_image_sizeaffine_trans_image_sizeAffineTransImageSizeAffineTransImageSizeAffineTransImageSizeaffine_trans_image_size

Module

Foundation

Operators