Scaling and Clipping Images

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Scaling Images

By default, images (such as JPEG, PNG, BMP, SVG) that are placed in panels are not scaled. This section demonstrates the four different scaling options available.

Here's a multi-panel figure with four panels, to contain the images. In each case, we'll use the copy of the R logo contained in the multipanelfigure package. This is a PNG file, 800 pixels wide and 700 pixels high, with a resolution of 300 dots per inch (DPI). That gives it a native size of 2.67" by 2.33".

library(multipanelfigure) figure <- multi_panel_figure( width = c(1, 5), height = c(1, 1, 4), unit = "inches") r_logo <- system.file("extdata/Rlogo.png", package = "multipanelfigure")

By default, the image is not rescaled, which means that only the central part of the image is displayed.

(figure %<>% fill_panel(r_logo))

By setting scaling = "stretch", all the image is displayed, fitting the panel exactly, but the height-to-width ratio had been altered, distorting the image.

(figure %<>% fill_panel(r_logo, scaling = "stretch"))

Setting scaling = "fit" means that the image is shrunked or grown so that it just fits inside the panel without the height-to-width ratio being distorted.

(figure %<>% fill_panel(r_logo, scaling = "fit"))

Setting scaling = "shrink", works the same way as scaling = "fit" when the image is larger than the panel.

(figure %<>% fill_panel(r_logo, scaling = "shrink", row = 3, column = 1))

If the image is smaller than the panel, scaling = "shrink" works like scaling = "none".

(figure %<>% fill_panel(r_logo, scaling = "shrink", row = 2:3, column = 2))

Clipping Plots and Images

By default, plots and images are clipped so that they don't overrun the panel that they were put in. (See, for example, Panel A in the previous plot.) To demonstrate the effect of clipping, let's use a 3 by 3 multi-panel figure, and fill all but the centre panel.

library(grid) figure2 <- multi_panel_figure( width = rep.int(1.25, 3), height = rep.int(1.25, 3), unit = "inches") rhino <- system.file("extdata/rhino.jpg", package = "multipanelfigure") for(position in list(c(1, 1), c(1, 2), c(1, 3), c(2, 1), c(2, 3), c(3, 1), c(3, 2), c(3, 3))) { figure2 %<>% fill_panel( rectGrob(gp = gpar(fill = "#91A45E")), row = position[1], column = position[2]) } figure2

When we try to display the rhino, only the central part of the image is shown, since there is no rescaling, and the panel isn't big enough.

(figure2 %>% fill_panel(rhino))

To turn off clipping, set panel_clip = "off". This time the complete image of the rhino is displayed, overrunning the other panel regions.

(figure2 %>% fill_panel(rhino, panel_clip = "off"))