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")

## Warning in check_units(width, unit): Multiple grid::units detected. Casting all
## to 'unit' argument ('inches').

## Warning in check_units(height, unit): Multiple grid::units detected. Casting all
## to 'unit' argument ('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))

## Setting row to 1

## Setting column to 1

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 row to 1

## Setting column to 2

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 row to 2

## Setting column to 1

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")

## Warning in check_units(width, unit): Multiple grid::units detected. Casting all
## to 'unit' argument ('inches').

## Warning in check_units(height, unit): Multiple grid::units detected. Casting all
## to 'unit' argument ('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))

## Setting row to 2

## Setting column to 2

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"))

## Setting row to 2

## Setting column to 2