geometry: Geometry Helpers

Description

ImageMagick uses a handy geometry syntax to specify coordinates and shapes for use in image transformations. You can either specify these manually as strings or use the helper functions below.

Usage

geometry_point(x, y)
geometry_area(width = NULL, height = NULL, x_off = 0, y_off = 0)
geometry_size_pixels(width = NULL, height = NULL, preserve_aspect = TRUE)
geometry_size_percent(width = 100, height = NULL)

Arguments

x: left offset in pixels
y: top offset in pixels
width: in pixels
height: in pixels
x_off: offset in pixels on x axis
y_off: offset in pixels on y axis
preserve_aspect: if FALSE, resize to width and height exactly, loosing original aspect ratio. Only one of percent and preserve_aspect may be TRUE.

Details

See ImageMagick Manual for details about the syntax specification. Examples of geometry strings:

"500x300" -- Resize image keeping aspect ratio, such that width does not exceed 500 and the height does not exceed 300.
"500x300!" -- Resize image to 500 by 300, ignoring aspect ratio
"500x" -- Resize width to 500 keep aspect ratio
"x300" -- Resize height to 300 keep aspect ratio
"50%x20%" -- Resize width to 50 percent and height to 20 percent of original
"500x300+10+20" -- Crop image to 500 by 300 at position 10,20

Examples

Run this code

# Specify a point
logo <- image_read("logo:")
image_annotate(logo, "Some text", location = geometry_point(100, 200), size = 24)

# Specify image area
image_crop(logo, geometry_area(300, 300), repage = FALSE)
image_crop(logo, geometry_area(300, 300, 100, 100), repage = FALSE)

# Specify image size
image_resize(logo, geometry_size_pixels(300))
image_resize(logo, geometry_size_pixels(height = 300))
image_resize(logo, geometry_size_pixels(300, 300, preserve_aspect = FALSE))

# resize relative to current size
image_resize(logo, geometry_size_percent(50))
image_resize(logo, geometry_size_percent(50, 20))

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