Hi everyone
can anyone help me with this problem?
I have several of these irregular shaped areas. Now I would need to calculate the midpoint of the areas in question.
Does anyone have a tutorial or similar how I could do that?
the picture below is an example:
Thanks a lot
Cheers
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Hi Michael
I'm wondering what criteria you would use to decide on the midpoint? I keep coming back to it being half way between the extremities when considering the object as a rectangle. If you were to select the area and copy to a new layer. Using Free Transform would place the centre handle at that half way point. Making a copy and reducing it in size, will cause it to reduce around that same centre handle.
I don't think this can be what you are looking for, so it would help — me at least — to know what criteria you want to use.
If you want to find the centre of gravity - which would normally be considered the midpoint of an irregular shape, you can do it in Photoshop although it is a little awkward.
1. Draw around your shape with the pen tool to create a shape and fill it with a solid color. Then turn off your image layer.
2. Use Select color range to make a selection of your color and in the histogram, expanded view, ensure Cache level is 1 (if not click the triangle at the top right of the histogram). Then read the number of pixels (in my case 4836668)
3. Calculate half that number of pixels - so for me 2418334
4. Add a white rectangle shape just above the irregular shape layer and position the edge approximately halfway down.
5. Press Ctrl+D to Deselect and select color range again
6.Read the number of pixels in the histogram - remember you must be at cache level 1 so click the warning triangle if not.
7. Move the white rectangle up/down and repeat steps 5 & 6 until you have as close as possible half the pixels as calculated in 3.
8. Drag a guide from the ruler an position it on the edge
9. Move the rectangle so it's vertical edge is across the shape and repeat steps 4-8
10. Your guides are in the centre of gravity so you can now turn off the shape layers and turn the image back on
Like I said - it is a bit awkward - but it does work.
I hope that helps
Dave
The below Script intends to mark that point for a black area on white with two guides (no guarantees, though).
// mark »center« on black are on white.
// based on paul riggott’s code for raw image assessment;
// 2018, use it at your own risk;
#target photoshop
File.prototype.readByte = function() {
return this.read(1).charCodeAt(0);
};
if (app.documents.length > 0) {
var originalRulerUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;
var myDocument = app.activeDocument;
var theDup = myDocument.duplicate ("dup", true);
theDup.changeMode (ChangeMode.GRAYSCALE);
theDup.layers[0].posterize(2);
theDup.selection.load(theDup.channels[0], SelectionType.REPLACE, true);
theDup.selection.expand(2);
var theBounds = theDup.selection.bounds;
theDup.crop(theBounds);
theDup.changeMode (ChangeMode.LAB);
var theResult = somethingSomething();
theDup.close (SaveOptions.DONOTSAVECHANGES);
activeDocument = myDocument;
myDocument.guides.add(Direction.VERTICAL, theResult[4] + theBounds[0]);
myDocument.guides.add(Direction.HORIZONTAL, theResult[5] + theBounds[1]);
app.preferences.rulerUnits = originalRulerUnits;
};
//////////////////
function convertByteToSignedByte(num){
var dec = (num | (num % 256))-128
return dec;
};
function convertByteToLum( num){
var dec = Math.round((num/256)*100);
return dec;
};
// get arrays of sums of non-white pixels per line and column;
function somethingSomething (){
if(!documents.length) return;
if(activeDocument.mode != DocumentMode.LAB) {
alert("Please convert this document to Lab mode\r Then re-run this script");
return;
};
var Name = decodeURI(app.activeDocument.name).replace(/\.[^\.]+$/, '');
try{
var Path = activeDocument.path;
}catch(e){var Path = '~/Desktop';}
var rawFile = new File(Path +"/"+Name +".raw");
saveAsRaw(rawFile);
var len = 0;
var W = activeDocument.width.as('px');
CountW=0;
CountH=0;
rawFile.encoding = 'BINARY';
rawFile.open('r');
// result arrays;
var theLines = new Array;
var theColumns = new Array;
for (var y = 0; y < W; y++) {theColumns.push(0)};
var theLine = 0;
////// work through //////
while(!rawFile.eof){
var theL = 100-(convertByteToLum(rawFile.readByte()));
var theA = convertByteToSignedByte(rawFile.readByte());
var theB = convertByteToSignedByte(rawFile.readByte());
len++;
theColumns[CountW] = theColumns[CountW]+theL/100;
// new line;
if(len % W == 0){
theLines.push(theLine);
theLine = 0;
CountH++;
CountW=0;
}else{
CountW++;
theLine = theLine + (theL/100);
};
};
// remove raw file;
rawFile.close();
rawFile.remove();
var theSum = 0;
var theSumColumn = 0;
for (var x = 0; x < theLines.length; x++) {theSum = theSum + theLines
}; for (var x = 0; x < theColumns.length; x++) {theSumColumn = theSumColumn + theColumns
}; var resultHor = midValue (theLines, theSum);
var resultVer = midValue (theColumns, theSumColumn);
activeDocument.guides.removeAll();
activeDocument.guides.add(Direction.VERTICAL, resultVer);
activeDocument.guides.add(Direction.HORIZONTAL, resultHor);
// return results;
return [theLines, theSum, theColumns, theSumColumn, resultVer, resultHor]
};
function saveAsRaw(file) {
var desc1 = new ActionDescriptor();
var desc2 = new ActionDescriptor();
desc2.putString( charIDToTypeID('FlCr'), "8BIM" );
desc2.putBoolean( charIDToTypeID('ChnI'), true );
desc1.putObject( charIDToTypeID('As '), charIDToTypeID('Rw '), desc2 );
desc1.putPath( charIDToTypeID('In '), new File( file ) );
desc1.putBoolean( charIDToTypeID('Cpy '), true );
executeAction( charIDToTypeID('save'), desc1, DialogModes.NO );
};
//////
function midValue (theArray, theSum) {
var theX = 0;
var theHalf = theSum/2;
for (var n = 0; n < theArray.length; n++) {
theX = theX + theArray
; if (theX == theHalf) {return n+1};
if (theX > theHalf) {
var thePercentage = theX/theSum;
var theDiff = 0.5 + ( ( (theSum - theX) / theSum) - ( (theX - theArray
) / theSum) ) * 0.5 / (theArray / theSum); return n+theDiff};
};
};
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