GDI Plus Image Histogram

#include <GDIP.au3>
#include <Array.au3>
#include <GUIConstants.au3>


Global $iSampleRate = 20000 ; Number of pixels read for histogram, the higher the more accurate but slower.
Global $histos, $histo

$gui = GUICreate("Histogram",278,200,-1,-1)
$pen = GuiCtrlCreateGraphic(10,10, 258, 150)
GUICtrlSetBkColor(-1,0xFFFFFF)

GUICtrlCreateLabel("Sample Rate:",20,160)
$sample = GUICtrlCreateInput($iSampleRate,20,175,70,20)

;GUICtrlSetState(-1, $GUI_DISABLE)
$BtnOpen= GUICtrlCreateButton("Open", 180, 165, 78, 30)
GUISetState()

While 1
Switch GUIGetMsg()
Case $BtnOpen
_main()

Case $GUI_EVENT_CLOSE
_GDIPlus_ShutDown()
Exit

EndSwitch
WEnd

Func _main()
Local $tmp
$iSampleRate = GUICtrlRead($sample)
If $tmp < 1 and $tmp > 99999999 Then
GUICtrlSetData($sample,10000)
$iSampleRate = 10000
EndIf
Local $sFile = FileOpenDialog("Open File", @WorkingDir, "All Picture Files (*.bmp;*.gif;*.jpg;*.jpeg;*.tif;*.tiff;*.png)", 3)
Local $t = TimerInit()
$aArrayHist = _Histogram($sFile, $iSampleRate)
Local $d = Round(TimerDiff($t)/1000,2)
ConsoleWrite("Time to build histogram = " & $d & @CRLF)
RenderHistogram($aArrayHist)
Local $d = Round(TimerDiff($t)/1000,2)
ConsoleWrite("Total Time = " & $d & @CRLF)
EndFunc

Func RenderHistogram($a)
Local $max = _ArrayMax($a,1,1)
GuiCtrlDelete($pen)
$pen=GuiCtrlCreateGraphic(10,10, 258, 150)
GUICtrlSetBkColor(-1,0xFFFFFF)
GUICtrlSetState(-1, $GUI_DISABLE)
For $i = 1 To UBound($a)-1
GUICtrlSetGraphic($pen,$GUI_GR_MOVE, $i,150)
GUICtrlSetGraphic($pen,$GUI_GR_LINE, $i,150 - Round(140*($a[$i]/$max),0))
Next
GUICtrlSetColor(-1,0x000000)
EndFunc

Func _Histogram($fImage, $iSampleRate)
If $fImage = "" Then Return SetError(1, 0, 0)
If Not FileExists($fImage) Then Return SetError(2, 0, 0)

Local $fName = StringRegExpReplace($fImage, ".*\\(.*).{4}", "$1")
Local $declared = True
If Not $ghGDIPDll Then
_GDIPlus_Startup()
$declared = False
EndIf
Local $hImageFromFile = _GDIPlus_ImageLoadFromFile($fImage)
Local $iWidth = _GDIPlus_ImageGetWidth($hImageFromFile)
Local $iHeight = _GDIPlus_ImageGetHeight($hImageFromFile)

Local $ratio
If $iWidth*$iHeight > $iSampleRate Then
$ratio = $iWidth/$iHeight
$iW = Int(Sqrt($iSampleRate*$ratio))
$iH = Int(sqrt($iSampleRate/$ratio))
Else
$iW = $iWidth
$iH = $iHeight
EndIf

Local $hImageThumbnail = DllCall($ghGDIPDll, "uint", "GdipCreateBitmapFromScan0", "int", $iW, "int", $iH, "int", 0, "int", 0x0026200A, "ptr", 0, "int*", 0)
If @error Then Return SetError(3, 0, 0)
$hImageThumbnail = $hImageThumbnail[6]
Local $hBmpCtxt = _GDIPlus_ImageGetGraphicsContext($hImageThumbnail)
DllCall($ghGDIPDll, "uint", "GdipSetInterpolationMode", "handle", $hBmpCtxt, "int", 7)
_GDIPlus_GraphicsDrawImageRect($hBmpCtxt, $hImageFromFile, 0, 0, $iW, $iH)
_GDIPlus_ImageDispose($hImageFromFile)
_GDIPlus_GraphicsDispose($hBmpCtxt)

; If you don't want to transfer to greyscale then comment out below
;#CS
$hImageContext = _GDIPlus_ImageGetGraphicsContext($hImageThumbnail)
Local $tNegMatrix, $pNegMatrix
$tNegMatrix = _GDIPlus_ColorMatrixCreateGrayScale()
$pNegMatrix = DllStructGetPtr($tNegMatrix)
$hIA = _GDIPlus_ImageAttributesCreate()
_GDIPlus_ImageAttributesSetColorMatrix($hIA, 0, True, $pNegMatrix)
_GDIPlus_GraphicsDrawImageRectRectIA($hImageContext, $hImageThumbnail, 0, 0, $iW, $iH, 0, 0, $iW, $iH, $hIA)
_GDIPlus_ImageAttributesDispose($hIA)
_GDIPlus_GraphicsDispose($hImageContext)
;#CE

$aHist = _BuildHistogramArray($hImageThumbnail)
_GDIPlus_ImageDispose($hImageThumbnail)
_GDIPlus_Shutdown()
Return $aHist
EndFunc

Func _BuildHistogramArray($hBitmap)

Local $tArgb, $pArgb, $aRet, $blue, $red, $green, $w, $h
$tArgb = DllStructCreate("dword Argb")
$pArgb = DllStructGetPtr($tArgb)

Local $Hist[257]
For $i = 0 To UBound($Hist) - 1
$Hist[$i] = 0
Next

$w = _GDIPlus_ImageGetWidth($hBitmap)
$h = _GDIPlus_ImageGetHeight($hBitmap)
ConsoleWrite("Thumbnail W = " & $w & @CRLF & "Thumbnail H = " & $h & @CRLF)

;-------------Use the following if you've changed the bitmap thumbnail to greyscale otherwise comment out and use the next one----------
For $i = 1 To $h
For $j = 1 To $w
$aRet = DllCall($ghGDIPDll, "int", "GdipBitmapGetPixel", "hwnd", $hBitmap, "int", $j, "int", $i, "ptr", $pArgb)
$Hist[Dec(Hex(DllStructGetData($tArgb, "Argb"),2))+1] +=1
$Hist[0] += 1
Next
Next

;-------------If you're keeping bitmap as RGB and not Greyscale then use below to build Array for Histogram------------------------------
#cs
For $i = 1 To $h
For $j = 1 To $w
$aRet = DllCall($ghGDIPDll, "int", "GdipBitmapGetPixel", "hwnd", $hBitmap, "int", $j, "int", $i, "ptr", $pArgb)
$color_hex = "0x" & Hex(DllStructGetData($tArgb, "Argb") ,6)
$Hist[Round((BitAND($color_hex,255) + BitShift(BitAND($color_hex,65280),0x08) + BitShift(BitAND($color_hex,16711680),0x10))/3,0)+1] += 1
$Hist[0] += 1
Next
Next
#ce
$Hist[2] = ($Hist[1] + $Hist[3])/2
ConsoleWrite("Total Count = " & $Hist[0] & @CRLF)
Return $Hist

EndFunc

Func ScaleImage($hImage, $iScaleW, $iScaleH, $iInterpolationMode = 7) ;coded by UEZ 2012
Local $iWidth = _GDIPlus_ImageGetWidth($hImage) * $iScaleW
Local $iHeight = _GDIPlus_ImageGetHeight($hImage) * $iScaleH
Local $hBitmap = DllCall($ghGDIPDll, "uint", "GdipCreateBitmapFromScan0", "int", $iWidth, "int", $iHeight, "int", 0, "int", 0x0026200A, "ptr", 0, "int*", 0)
If @error Then Return SetError(3, 0, 0)
$hBitmap = $hBitmap[6]
Local $hBmpCtxt = _GDIPlus_ImageGetGraphicsContext($hBitmap)
DllCall($ghGDIPDll, "uint", "GdipSetInterpolationMode", "handle", $hBmpCtxt, "int", $iInterpolationMode)
_GDIPlus_GraphicsDrawImageRect($hBmpCtxt, $hImage, 0, 0, $iWidth, $iHeight)
_GDIPlus_ImageDispose($hImage)
_GDIPlus_GraphicsDispose($hBmpCtxt)
Return $hBitmap
EndFunc