Area calculation

[Armand]

Hi,

I've attached an example picture of a shape which i would like to calculate it's area. Let's say a user has marked this kind of shaped area on the screen and you need to run some calculations on it, like getting the area of it.

- How would you go about this problem?

Thanks in advance

[Valuater]

"an example picture of a shape which i would like to calculate it's area."

 

I see a rectangle... L x W = Area

Tada!!  8)

[SadBunny]

This is too vague. What do you mean exactly be area? The amount of black pixels? The amount of cm2? And what do you mean by "a user has marked this"? Does that mean you have the coordinates, dimensions and radii of the involved geometric shapes? (From the looks of it, two circles, a rectangle and a triangle...)

[Armand]

@Valuater great response, way to go!
@SadBunny I have the whole coordinates and i need to calculate the area - by that i mean the number of pixels - I can convert these to whatever I want afterwards anyway.

I can also see circles and rectangles and such but how to i make a code to analyze and calculate that?!

[BrewManNH]

You'd be better off asking this question on a math or drafting forum rather than here. I don't see how this would pertain to AutoIt until you have the math or the algorithm needed to do it.

[jchd]

Given that in the example case one has several geometric 2nd degree shapes (one could be considered a circle but another is clearly an ellipsis) partly overlapping asymetrically, I bet my keyboard that the mathematical solution will be either very complex or too complex to be expressed in what maths call "elementary functions". For instance, just computing the common part between the ellipsis and the square (admit it is one) is awful.

For the well-known goat and field problem (involving just two overlapping circles), see http://mathforum.org/library/drmath/view/51746.html
It was only in 1995 that a closed-form solution was discovered by Shepherd and van Eetvelt.

I'd go for the pedestrian way which is guaranteed to work whatever image is given: examine the bitmap row after row and accumulate the black pixels.

[nitekram]

I may not know what I am talking about, but if the pic above is an example, and the colors are going to be that dramatic, then why not just count the pixels in the image (all the same color) then figure out how many pixels are in a inch squared, and then create a ratio to solve

 

Actually after reading @jchd's last comment, I think we are on the same page

Edited April 30, 2015 by nitekram
spelling

[iamtheky]

same.

[Malkey]

This example has the black area of the image containing 258668 pixels = 181.078826909677 square centimeters

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#include <GDIPlus.au3>
#include <Array.au3>
#include <WinAPI.au3>
; http://www.autoitscript.com/forum/topic/131661-gdi-image-file-to-2d-array-and-vice-versa/page__view__findpost__p__917176
Opt("MustDeclareVars", 1)
Local $iW, $iH
_GDIPlus_Startup()
Dim $pixelarray, $iCounta, $iCountb
Local $file_in = "area_thumb.png" ; "Bckgrnd.jpg" ; "image1-before.jpg" ;
Local $file_out = "area_after.jpg"
_ImageFileToNumberWhitePixels($file_in, $pixelarray)
_GDIPlus_Shutdown()

Func _ImageFileToNumberWhitePixels($filename, ByRef $aArray)
    Local $Reslt, $stride, $format, $Scan0, $hImage
    Local $v_Buffer, $width, $height
    Local $i, $j

    $hImage = _GDIPlus_ImageLoadFromFile($filename)
    $iW = _GDIPlus_ImageGetWidth($hImage)
    $iH = _GDIPlus_ImageGetHeight($hImage)
    $Reslt = _GDIPlus_BitmapLockBits($hImage, 0, 0, $iW, $iH, $GDIP_ILMREAD, $GDIP_PXF32ARGB)
    ;Get the returned values of _GDIPlus_BitmapLockBits ()
    $width = DllStructGetData($Reslt, "width")
    $height = DllStructGetData($Reslt, "height")
    $stride = DllStructGetData($Reslt, "stride")
    $format = DllStructGetData($Reslt, "format")
    $Scan0 = DllStructGetData($Reslt, "Scan0")

    For $i = 0 To $iW - 1
        For $j = 0 To $iH - 1
            $v_Buffer = DllStructCreate("dword", $Scan0 + ($j * $stride) + ($i * 4))
            If Hex(DllStructGetData($v_Buffer, 1), 8) == "FFFFFFFF" Then
                $iCounta += 1
            Else
                $iCountb += 1
            EndIf
        Next
    Next
    _GDIPlus_BitmapUnlockBits($hImage, $Reslt)
    _GDIPlus_ImageDispose($hImage)

    ConsoleWrite("Width x Height = " & $iW & "x" & $iH & " = " & ($iW * $iH) & @LF)
    ConsoleWrite("WHite pixels + Non-white pixels  = " & $iCounta & " +  " & $iCountb & " = " & $iCounta + $iCountb & @LF)
    ConsoleWrite("Number of non-white pixels = " & $iCountb & @LF)
    ; Ref http://www.translatorscafe.com/cafe/units-converter/typography/calculator/pixel-%28X%29-to-centimeter-%5Bcm%5D/
    ConsoleWrite("If 1 pixel  = 0.02645833333333cm (x) x 0.02645833333333cm (y) , then" & @LF & $iCountb & " pixels = " & (0.2645833333333 * 0.2645833333333 * $iCountb) & " square centimeters " & @LF)
    Return
EndFunc   ;==>_ImageFileToNumberWhitePixels

Edit: Replaced 18107.8826909677 square centimeters

Edited April 30, 2015 by Malkey
Deciminal in wrong place. Definitely not a metre by a metre.