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My scripts that use HighlightImage stopped working after upgrading to 12. I discovered that HighlightImage doubles the Dimensions of the image, see below. Bug ?? workaround ? I need the exact same image as the original, only with a marker superimposed.

enter image description here

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  • $\begingroup$ This doesn't happen for me on 12.1.1 Windows 10. Try Options[img2, PlotRange] to see if it's inflating the plot range. It's either that, or the image is scaled after marking it. $\endgroup$
    – flinty
    Commented Jul 28, 2020 at 21:59
  • $\begingroup$ I'm not sure this warrants the bugs tag. I have a feeling this is by design. $\endgroup$
    – Greg Hurst
    Commented Mar 10, 2023 at 13:52

1 Answer 1

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HighlightImage returns a Graphics object, not an Image.

HighlightImage[img, {120, 120}] // Head

Graphics

When you call ImageDimensions, Rasterize is invoked internally to create an Image object to find the dimensions of. I believe it was V12 that Rasterize got an overhaul to work with high dpi screens.

A regular screen is 72 dpi (or 96 on Windows I think). Modern macs are 144 though:

$OperatingSystem

"MacOSX"

CurrentValue["ConnectedDisplays"]

{{"Region" -> {{0., 1680.}, {23., 1050.}}, 
 "FullRegion" -> {{0., 1680.}, {0., 1050.}}, 
 "PixelDimensions" -> {3360, 2100}, "BitDepth" -> 32, 
 "Resolution" -> 144., "Scale" -> 2.}}

We can fix this by calling Rasterize with a custom dpi setting:

img2 = Rasterize[im, ImageResolution -> 72];
ImageDimensions[img2]

{240, 240}
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  • $\begingroup$ Thank you so much for that, Chip ! I was pulling my hair out. I am close to a hard deadline and this was going to kill me dead, $\endgroup$
    – Eric
    Commented Jul 29, 2020 at 1:41

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