The image pattern - filling a geom with an image from file or URL
This pattern will load an image from a file or URL (pattern_filename) and display it within the geom.
Because the image will most likely not exactly cover the area of the geom, there are options to specify how the image is used to fill the region.
After expanding to cover the area, the image is then clipped to the boundary of the geom.
The files/URLs are loaded with magick::image_read which means that transparent images and SVGs are supported.
image options
| Aesthetic | Description | Default |
|---|---|---|
pattern_filename |
Image filename or URL | ’’ |
pattern_type |
Image scaling type | ‘fit’ |
pattern_scale |
Extra scaling | 1 |
pattern_gravity |
Position of image within area | ‘center’ |
pattern_filter |
Filter to use when scaling | ‘lanczos’ |
pattern_alpha |
Alpha | NA |
pattern_aspect_ratio |
Override aspect ratio | NA |
pattern_key_scale_factor |
Additional scale factor for legend | 1 |
pattern_type |
Description | pattern_scale |
pattern_gravity |
|---|---|---|---|
| squish | distort the image to cover the bounding box of the region | ||
| fit | scale the image such that either the width or the height of the image fits in the bounding box. | Yes | |
| expand | scale the image beyond the bounding box and crop it such that the image fully covers the width and the height of the region | ||
| none | position a single image in the region without attempting to scale to the bounding box size | Yes | Yes |
| tile | repeat the image to cover the bounding box. | Yes |
Note: not all combinations of aesthetics are useful e.g. if pattern_type = 'fit' is specified, then pattern_scale has no effect.
Example Data
These examples use some of the built-in images in the ggpattern package.
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# filenames of images
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
logo_filename <- system.file("img", "Rlogo.png" , package="png")
magpie_filename <- system.file("img", "magpie.jpg", package="ggpattern")
bug_filename <- system.file("img", "bug.jpg" , package="ggpattern")
seamless1 <- system.file("img", "seamless1.jpg" , package="ggpattern")
seamless2 <- system.file("img", "seamless2.jpg" , package="ggpattern")
seamless3 <- system.file("img", "seamless3.jpg" , package="ggpattern")
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Plotting data
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
df1 <- data.frame(
trt = c("a", "b", "c"),
outcome = c(2.3, 1.9, 3.2),
gravity = c('South', 'North', 'West'),
filltype = c('squish', 'fit' , 'expand'),
scale = c(1, 2, 0.5),
filename = c(logo_filename, magpie_filename, bug_filename),
stringsAsFactors = FALSE
)| trt | outcome | gravity | filltype | scale | filename |
|---|---|---|---|---|---|
| a | 2.3 | South | squish | 1.0 | /Library/Frameworks/R.framework/Versions/4.1/Resources/library/png/img/Rlogo.png |
| b | 1.9 | North | fit | 2.0 | /private/var/folders/5p/78cv9fvn4xn_rbgxpx51q5n80000gn/T/RtmpactFlY/temp_libpath2f2230a3ba7/ggpattern/img/magpie.jpg |
| c | 3.2 | West | expand | 0.5 | /private/var/folders/5p/78cv9fvn4xn_rbgxpx51q5n80000gn/T/RtmpactFlY/temp_libpath2f2230a3ba7/ggpattern/img/bug.jpg |
Example: pattern = 'image' - No Attempt at filling the area (pattern_type = 'none')
If pattern_type = 'none' then no attempt is made at snugly filling the area. Instead a single copy of the image is scaled (pattern_scale) and placed (pattern_gravity) in the geom area.
ggplot(df1, aes(trt, outcome)) +
geom_col_pattern(
aes(
fill = trt,
pattern_gravity = I(gravity),
pattern_scale = I(scale)
),
pattern = 'image',
pattern_filename = logo_filename,
pattern_type = 'none',
colour = 'black'
) +
theme_bw(15) +
labs(
title = "ggpattern::geom_col_pattern()",
subtitle = "pattern = 'image', pattern_type = 'none'"
) +
theme(legend.key.size = unit(1.5, 'cm')) +
coord_fixed(ratio = 1/2)
Example: pattern = 'image' - Covering the area (pattern_type = 'fit', 'squish', 'expand')
In the plot below, 3 different methods are used to cover the area of the geom. From left-to-right:
-
pattern_type = 'squish'to force the image to cover the bounding box of the geom. -
pattern_type = 'fit'to force the image to cover the width (or height) yet still remain fully visible.pattern_gravity = 'North'floats the image to the top. -
pattern_type = 'expand`` scales the image (while preserving aspect ratio) such that the entire geom is covered.pattern_gravity = ‘West’` anchors the image to the left side of the geom.
ggplot(df1, aes(trt, outcome)) +
geom_col_pattern(
aes(
fill = trt,
pattern_gravity = I(gravity),
pattern_type = I(filltype)
),
pattern = 'image',
colour = 'black',
pattern_filename = logo_filename,
) +
theme_bw(15) +
labs(
title = "ggpattern::geom_col_pattern()",
subtitle = "pattern = 'image'"
) +
# theme(legend.key.size = unit(1.5, 'cm')) +
theme(legend.position = 'none') +
coord_fixed(ratio = 1/2)
Example: pattern = 'image' - Tiling (pattern_type = 'tile')
When tiled, the image is replicated in order to cover the entire area of the geom. In this example, pattern_scale is also applied to the image so that it appears at different sizes.
ggplot(df1, aes(trt, outcome)) +
geom_col_pattern(
aes(
fill = trt,
pattern_gravity = I(gravity),
pattern_scale = I(scale)
),
pattern = 'image',
pattern_type = 'tile',
pattern_filename = logo_filename,
colour = 'black'
) +
theme_bw(15) +
labs(
title = "ggpattern::geom_col_pattern()",
subtitle = "pattern = 'image', pattern_type = 'tile'"
) +
# theme(legend.key.size = unit(1.5, 'cm')) +
theme(legend.position = 'none') +
coord_fixed(ratio = 1/2)
Example: pattern = 'image' - Tiling with seamless patterns
By choosing a seamlessly tiling image, then a tiled fill will not have visible discontinuities.
ggplot(mtcars) +
geom_density_pattern(
aes(
x = mpg,
pattern_filename = as.factor(cyl)
),
pattern = 'image',
pattern_type = 'tile'
) +
theme_bw(15) +
theme(legend.key.size = unit(1.5, 'cm')) +
labs(
title = "ggpattern::geom_density_pattern()",
subtitle = "pattern = 'image', pattern_type = 'tile'"
) +
scale_pattern_filename_manual(values = c(`4` = seamless1, `6` = seamless2, `8` = seamless3)) +
coord_fixed(ratio = 80)
Example: pattern = 'image' - Tiling with seamless patterns (with scaling)
ggplot(mtcars) +
geom_density_pattern(
aes(
x = mpg,
pattern_filename = as.factor(cyl)
),
pattern = 'image',
pattern_type = 'tile',
pattern_scale = 0.5
) +
theme_bw(15) +
theme(legend.key.size = unit(2, 'cm')) +
labs(
title = "ggpattern::geom_density_pattern()",
subtitle = "pattern = 'image', pattern_type = 'tile'"
) +
scale_pattern_filename_manual(values = c(`4` = seamless1, `6` = seamless2, `8` = seamless3)) +
coord_fixed(ratio = 80)
Example: pattern = 'image' - Tiling with fit to width (of element bounding box)
In a common case, the image to be tiled should be first scaled to the width of the bar to be tiled and then tiling appears like a vertical stacking. This is useful for bar charts.
Specify pattern_scale = -1 to fit the width of the geom, and pattern_scale = -2 to fit the height of the geom.
ggplot(df1, aes(trt, outcome)) +
geom_col_pattern(
aes(
fill = trt,
pattern_filename = I(filename)
),
pattern = 'image',
pattern_type = 'tile',
pattern_scale = -1,
colour = 'black'
) +
theme_bw(15) +
labs(
title = "ggpattern::geom_col_pattern()",
subtitle = "pattern = 'image', pattern_type = 'tile',\npattern_scale = -1"
) +
theme(legend.position = 'none') +
coord_fixed(ratio = 1)