http://imagej.273.s1.nabble.com/Straight-line-with-preset-length-macro-tp5014526p5014531.html
If you want to have also lines shorter than 500, don't recalculate x, y if 'enlargeFactor' is more than 1.
> Thank you for the responses, Herbie and Emanuele.
>
> I am new to ImageJ so I am not sure what "spatially discrete" images or
> "lines of arbitrary orientation" are. However, I'll try to describe what I
> have to do in more detail and maybe that'll explain what you want to know.
>
> The image that I have to work with is *1025x684 pixels*. Example image
> <
http://4.bp.blogspot.com/-Zo65_84L9Uc/UyCmC_uw0xI/AAAAAAAACCs/oxKFQtFl0hY/s1600/red-eye-frog-hd-photography-wallpapers78.jpg>
> with same resolution.
>
> Once opened, I proceed to change the units from *pixels to µm* (Image >
> Properties) as well as the *Pixel Width to 2.93* (Pixel Height and Voxel
> Depth also changes to 2.93 automatically). The 2.93 is just to make the
> *desired resolution roughly 3000x2000 µm* (3003.25x2004.12 µm to be exact).
>
> I found a macro provided by Wayne Rasband ( Thread
> <
http://imagej.1557.x6.nabble.com/how-to-stop-the-freehand-lines-tool-at-a-set-distance-20-um-td3690197.html>
> )
>
> macro "Set Length Line Tool - C00bL1de0L1ee1" {
> *maxLength = 20;*
> leftClick=16
> i = 0;
> xpoints = newArray(2000);
> ypoints = newArray(2000);
> getCursorLoc(x2, y2, z, flags);
> xpoints[i]=x2; ypoints[i++]=y2;
> while (true) {
> getCursorLoc(x, y, z, flags);
> if (flags&leftClick==0) exit();
> if (x!=x2 || y!=y2) {
> xpoints[i] = x;
> ypoints[i] = y;
> i++;
> x2=x; y2=y;
> xpoints2 = Array.trim(xpoints, i);
> ypoints2 = Array.trim(ypoints, i);
> *makeSelection("freeline", xpoints2, ypoints2);*
> List.setMeasurements;
> length = List.getValue("Length");
> showStatus("length="+d2s(length,2));
> if (length>=maxLength) exit;
> }
> }
> }
>
> This macro allowed me to draw a *freeline* that'll stop at *20 µm*. However,
> I want to be able draw with the *straightline tool* that'll stop at *500
> µm*. Hence, I played around and changed the code to
>
> macro "Set Length Line Tool - C00bL1de0L1ee1" {
> *maxLength = 500;*
> leftClick=16
> i = 0;
> xpoints = newArray(1025);
> ypoints = newArray(684);
> getCursorLoc(x2, y2, z, flags);
> xpoints[i]=x2; ypoints[i++]=y2;
> while (true) {
> getCursorLoc(x, y, z, flags);
> if (flags&leftClick==0) exit();
> if (x!=x2 || y!=y2) {
> xpoints[i] = x;
> ypoints[i] = y;
> i++;
> x2=x; y2=y;
> xpoints2 = Array.trim(xpoints, i);
> ypoints2 = Array.trim(ypoints, i);
> *makeLine(288, 335, x2, y2);*
> List.setMeasurements;
> length = List.getValue("Length");
> showStatus("length="+d2s(length,2));
> if (length>=maxLength) exit;
> }
> }
> }
>
> This new macro allowed me to draw a *straightline* that'll stop roughly at
> *500 µm* starting at coordinates 288,335 (just a random coordinate I chose).
> However, the straightline never really stops at exactly 500 µm (length
> measurement shows 501.30 µm).
>
> Only after changing the *Known Distance to 500* in *Analyze > Set Scale*
> (with other info being Distance in Pixels: 171. Pixel aspect ratio: 1.0,
> Unit of length: µm, Scale: 0.342 pixels/µm) and making the y-coordinate
> constant (*makeLine(288, 335, x2, 335)*) will I be able to draw a straight
> line that stops at exactly 500 µm in length. This also changes the image
> resolution to 2997.08x2000.00 µm (which is fine).
>
> This macro is doable however, it becomes difficult/time consuming to do it
> this way when I have to repeat this process hundreds of times.
>
> I would like to know if the macro can be tweaked to allow me to draw a
> *straight line starting at any point on the image that can go in any
> direction and will stop at exactly 500 µm in length*.
>
> Sorry for the long reply. Thanks for reading/helping!
>
>
>
>
> --
> View this message in context:
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>
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