transform function

Image Transform

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

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.

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))

See Also

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