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POControlling the Rasterize[] width for notebook-related expressions
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copied!<p><strong>Update</strong> Mr Wizard's answer gives pixel-perfect results, but it is Windows-only and destroys the clipboard contents. My answer should work on any platform, but it's less precise: e.g. it omits In/Out labels. It does allow setting the rasterization width though.</p> <hr> <p>This problem came up when I was <a href="https://stackoverflow.com/a/8343460/695132">trying to make a preview window for an image uploader</a> (see the end of that answer).</p> <p>I would like to create a palette button that will upload the current notebook selection as an image. Before uploading, I would like to show a preview of the image, to reduce the chance of something going awry before contacting the server.</p> <p>This is what I have so far (includes only the preview code, not the uploader):</p> <pre><code>button = Button[ "Preview", Module[ {expr = NotebookRead@InputNotebook[]}, If[expr =!= {}, With[{img = Rasterize[expr]}, MessageDialog[ Column[{"Would you like to perform the action?", img}], {"Do it!" :> doIt[img], "Cancel" :> Null} ] ] ] ] ] </code></pre> <p><sup>In case you are wondering why I used a nested <code>With</code> inside the <code>Module</code> instead of making <code>img</code> a module-variable too: it's because by the time <code>doIt[img]</code> is evaluated, the local module variables will have been cleared, so I need to substitute the rasterized expression directly into the <code>doIt</code> function,</sup></p> <p>This button works (more or less). You can try it by creating a graphic in the same notebook (e.g. <code>Graphics[Circle[]]</code>), selecting it using a single click, then clicking the Preview button.</p> <p>However, if I put it in a palette using <code>CreatePalette[button]</code>, then the rasterization will happen for the window-width of the palette, and I get something like this:</p> <p><img src="https://i.stack.imgur.com/d3HzO.png" alt="Screenshot of the problem"></p> <p><strong>How can I control the width of rasterization, or more generally, how can I create a preview dialog for the uploader that avoids this issue?</strong></p> <p>For an additional improvement, it would be nice to be able to size the message window so it fits the preview image (and still shows the button: the button disappears with <code>WindowSize -> All</code>).</p> <hr> <h2>Answers</h2> <p><strong>Mr. Wizard's suggestion:</strong></p> <pre><code>button = Button[ "Preview", (FrontEndExecute[ FrontEndToken[FrontEnd`SelectedNotebook[], "CopySpecial", "MGF"]]; MessageDialog[ First@Cases[NotebookGet@ClipboardNotebook[], RasterBox[data_, ___] :> Image[data, "Byte", ColorSpace -> "RGB", Magnification -> 1], Infinity]])] CreatePalette[button] </code></pre> <p><strong>Problems:</strong> It (probably) only works on Windows, and it destroys the clipboard contents.</p>

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