pixRotate: Rotate or Transpose a Pix Image

In duncantl/Rtesseract: Interface to the tesseract OCR system

Rotate or Transpose a Pix Image

Description

These functions allow the caller to rotate a Pix image. This can either be done by rotating the pixels within the same rectangle, or by transposing the rows and columns of the rectangular image so that rows become columns and columns become rows. Both change the contents in a similar manner, but the resulting image has different dimensions in general.

The Flip functions reverse the order of the rows (TB) or the columns (LR). These are done quickly in leptonica rather than bringing the data back to R. These can also be done in place (i.e. modify the existing image), create a new image, or for a second image.

Usage

pixRotateAMGray(pix, angle, grayVal = 0L)
pixRotate(pix, angle = -pi/2, type = 1L, incolor = 1L, width = 0L, height = 0L)
pixFlipLR(pix, target = NULL)
pixFlipTB(pix, target = NULL)

Arguments

pix	the Pix object created via pixRead or GetImage
angle	a numeric value specifying the angle of rotation. These are in radians. Positive values are clockwise, negative values anti-clockwise
grayVal	an integer value specifying the ....
type	how to rotate - by area map, shear or sampling
incolor	whether to bring in white or black pixels the rotation leaves uncovered space from the background.
width,height	ignore for now, i.e. leave as 0
target	either a Pix object or NULL. If this is NULL, a new Pix object is created and returned. If this is a Pix object, this is used to hold the modified contents of the Pix. This can be pix itself in which case the flip is done in place, i.e., in the original image, overwriting the original contents.

Value

A new Pix object.

Note

In the future, we may allow the caller to do some of these operations in place, i.e. to modify the input image.

Author(s)

Duncan Temple Lang

References

Leptonica http://leptonica.com/ Tesseract https://code.google.com/p/tesseract-ocr/

See Also

pixRead

Examples

f = system.file("images", "SMITHBURN_1952_p3.png", package = "Rtesseract")
px = pixRead(f)

par(mfrow = c(2, 2))
plot(px)

pr = pixRotate(px)
plot(pr)

 # Here we flip the rows and columns of the image.
 # The result is that we have the "correct" dimensions for the new image
 # For the rotated image, the dimensions remain unchanged from the
 # original image.
pt = pixTranspose(px)
plot(pt)

 # We reverse the order of the columns.
pth = pixTranspose(px, horiz = TRUE)
plot(pth)

duncantl/Rtesseract documentation built on March 25, 2022, 5:50 a.m.