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How can I place a mark, like a cross-hair (to suggest "X marks the spot") and a text label associated with it, at a particular position on an image (mine in particular is Colorized)?

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3 Answers 3

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This is a simple way:

Show[
    Plot[Sin[x], {x, 0, 2 \[Pi]}],
    Graphics[{PointSize[Large], Red, Point[{3 \[Pi]/2, -1}],
    Black, Text["Minimum", {3 \[Pi]/2, -.8}]}]]

enter image description here

Edit

If you have an image created with Colorize you can apply the same method. In the example below img is the image you obtain by taking the first example given in the Help under Colorize.

Show[
   img,
   Graphics[{PointSize[Large], Red, Point[{20, 100}],
   White, Text["California", {30, 90}]}]]

enter image description here

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  • $\begingroup$ My image is created with Colorize and this gives Raster data contains 0 values per pixel; 3 or 4 are required with ColorFunction->RGBColor, even though it displays fine without the text. $\endgroup$
    – Emre
    Mar 30, 2012 at 18:34
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Another approach:

anXtoMarkTheSpot = Graphics[{
  White,
  Line[{{0,10}, {0, -10}}], 
  Line[{{-10,0}, {10, 0}}], 
  Text[Style["the Spot",14, Bold, White, 
      TextAlignment->Left],{20,5}]}, 
  ImageSize -> 80];

treasureMap = Colorize[ExampleData[{"TestImage", "Aerial2"}]];

ImageCompose[treasureMap, anXtoMarkTheSpot, {60,40}]

treasure map

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You can also use the Drawing Tools palette to annotate an image interactively. It can be invoked in three ways:

  1. Selecting Drawing Tools from the Graphics menu
  2. Using the short-cut Ctrl+D or
  3. Using the right-click context menu on a graphics object:

context menu -- drawing tools

For a detailed tutorial on the Drawing Tools palette see Interactive Graphics Palette. The following image from the tutorial summarizes the functions in the palette:

enter image description here

Usage example: palette states and before and after appearance of the image using the same image in vucko's answer:

enter image description here

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