transform {magick}

Image Transform

Description

Basic transformations like rotate, resize, crop and flip. The geometry syntax is used to specify sizes and areas.

Usage

image_trim(image, fuzz = 0)

image_chop(image, geometry)

image_rotate(image, degrees)

image_resize(image, geometry = NULL, filter = NULL)

image_scale(image, geometry = NULL)

image_sample(image, geometry = NULL)

image_crop(image, geometry = NULL, gravity = NULL, repage = TRUE)

image_extent(image, geometry, gravity = "center", color = "none")

image_flip(image)

image_flop(image)

image_deskew(image, threshold = 40)

image_deskew_angle(image, threshold = 40)

image_page(image, pagesize = NULL, density = NULL)

image_repage(image)

image_orient(image, orientation = NULL)

image_shear(image, geometry = "10x10", color = "none")

image_distort(image, distortion = "perspective", coordinates, bestfit = FALSE)

Arguments

image

magick image object returned by image_read() or image_graph()

fuzz

relative color distance (value between 0 and 100) to be considered similar in the filling algorithm

geometry

a geometry string specifying area (for cropping) or size (for resizing).

degrees

value between 0 and 360 for how many degrees to rotate

filter

string with filter type from: filter_types

gravity

string with gravity value from gravity_types.

repage

resize the canvas to the cropped area

color

a valid color string such as "navyblue" or "#000080". Use "none" for transparency.

threshold

straightens an image. A threshold of 40 works for most images.

pagesize

geometry string with preferred size and location of an image canvas

density

geometry string with vertical and horizontal resolution in pixels of the image. Specifies an image density when decoding a Postscript or PDF.

orientation

string to set image orientation one of the orientation_types. If NULL it applies auto-orientation which tries to infer the correct orientation from the Exif data.

distortion

string to set image orientation one of the distort_types.

coordinates

numeric vector (typically of length 12) with distortion coordinates

bestfit

if set to TRUE the size of the output image can be different from input

Details

For details see Magick++ STL documentation. Short descriptions:

• image_trim removes edges that are the background color from the image.

• image_chop removes vertical or horizontal subregion of image.

• image_crop cuts out a subregion of original image

• image_rotate rotates and increases size of canvas to fit rotated image.

• image_deskew auto rotate to correct skewed images

• image_resize resizes using custom filterType

• image_scale and image_sample resize using simple ratio and pixel sampling algorithm.

• image_flip and image_flop invert image vertically and horizontally

The most powerful resize function is image_resize which allows for setting a custom resize filter. Output of image_scale is similar to image_resize(img, filter = "point").

For resize operations it holds that if no geometry is specified, all frames are rescaled to match the top frame.

See Also

Other image: _index_, analysis, animation, attributes(), color, composite, defines, device, edges, editing, effects(), fx, geometry, morphology, ocr, options(), painting, segmentation, video

Examples

logo <- image_read("logo:")
logo <- image_scale(logo, "400")
image_trim(logo)
image_chop(logo, "100x20")
image_rotate(logo, 45)
# Small image
rose <- image_convert(image_read("rose:"), "png")

# Resize to 400 width or height:
image_resize(rose, "400x")
image_resize(rose, "x400")

# Resize keeping ratio
image_resize(rose, "400x400")

# Resize, force size losing ratio
image_resize(rose, "400x400!")

# Different filters
image_resize(rose, "400x", filter = "Triangle")
image_resize(rose, "400x", filter = "Point")
# simple pixel resize
image_scale(rose, "400x")
image_sample(rose, "400x")
image_crop(logo, "400x400+200+200")
image_extent(rose, '200x200', color = 'pink')
image_flip(logo)
image_flop(logo)
skewed <- image_rotate(logo, 5)
deskewed <- image_deskew(skewed)
attr(deskewed, 'angle')
if(magick_config()$version > "6.8.6")
  image_orient(logo)
image_shear(logo, "10x10")
building <- demo_image('building.jpg')
image_distort(building, 'perspective', c(7,40,4,30,4,124,4,123,85,122,100,123,85,2,100,30))