ExtFloodFill with custom scaling

Question

I'm filling irregular shapes with solid colors and my desired coord system is centered origin. I can make this work by setting scaleheight/width to max dimension of picturebox and computing offset=maxdimension/2. But this means every point must be specified as x+offest/y+offset; rather messy.

I can set up for 0/0 centered in pic via

dest.ScaleMode = vbInches 'here's the key; picture's scale mode is inches

dest.ScaleWidth = MaxDimension
dest.ScaleLeft = -dest.ScaleWidth / 2

dest.ScaleHeight = MaxDimension
dest.ScaleTop = -dest.ScaleHeight / 2

But extfloodfill cannot locate the proper fill point(fills from wrong point).

Answer 1

Some progress has been made! Using this to setup:

Pic2.ScaleMode = vbInches
SetMapMode Pic2.hDC, MM_ISOTROPIC
SetWindowExtEx Pic2.hDC, 1, 1, Null
SetViewportExtEx Pic2.hDC, GetDeviceCaps(Pic2.hDC, LOGPIXELSX), GetDeviceCaps(Pic2.hDC, LOGPIXELSY), Null

1,1 is to get inches. your code suggested 64,64 to get 1/64; doesn't make sense. I tried .5,.5 and 2,2, no change. my object is (-2..5,-2.5)-(2.5,2.5)

The object is drawn and extfloodfill works BUT is drawn at 4x size and the origin is at 0/0 (upperleft corner)

I added 1 line:

Pic2.ScaleMode = vbInches
SetMapMode Pic2.hDC, MM_ISOTROPIC
SetWindowExtEx Pic2.hDC, 1, 1, Null
SetViewportExtEx Pic2.hDC, GetDeviceCaps(Pic2.hDC, LOGPIXELSX), GetDeviceCaps(Pic2.hDC, LOGPIXELSY), Null
Pic2.Scale (-2.5, -2.5)-(2.5, 2.5)

Object size and positioning now proper but fill stops working

Answer 2

The object is not drawn at 4x size

You need SetStretchBltMode and StretchBlt.

the origin is not at 0/0.

You need SetViewportOrgEx.
Such as

case WM_PAINT:  
        {  
            PAINTSTRUCT ps;  
            HDC hdc = BeginPaint(hWnd, &ps);  
            // TODO: Add any drawing code that uses hdc here...  
			RECT rc{};  
			GetClientRect(hWnd, &rc);  
			SetMapMode(hdc, MM_ANISOTROPIC);  
			SetWindowExtEx(hdc, 1, 1, NULL);  
			int pixel_x = GetDeviceCaps(hdc, LOGPIXELSX);  
			int pixel_y = GetDeviceCaps(hdc, LOGPIXELSY);  
			SetViewportExtEx(hdc, pixel_x, -pixel_y, NULL);  
			SetViewportOrgEx(hdc, rc.right / 2, rc.bottom / 2, NULL);  
			  
			//POINT aptTriangle[] = { 0,50, 100,0,  0,-99, -25,0, 0,50 };  
			POINT aptTriangle[] = { 0,1, 1,0,  0,-1, -1,0, 0,1 };  
			Polyline(hdc, aptTriangle, ARRAYSIZE(aptTriangle));  
  
			HBRUSH hBrush = CreateHatchBrush(HS_DIAGCROSS, RGB(0, 0, 255));  
			//	' Select it for use in Form1, noting the previous brush.  
			HGDIOBJ hOldBrush = SelectObject(hdc, hBrush);  
			BOOL retval = FALSE;  
			//	' Flood fill the area outside the ellipse (use a green boundary)  
			retval = ExtFloodFill(hdc, 0, 2, Color::Black, FLOODFILLBORDER);//Picture 1  
  
			//	' Select the previously selected pen and brush.  
			SelectObject(hdc, hOldBrush);  
			//	' Delete the pen and brush to free up resources.  
			retval = DeleteObject(hBrush);  
            EndPaint(hWnd, &ps);  
        }  
        break;  

Note: ExtFloodFill has a int x and y. So ExtFloodFill(hdc, 0, 1.2, Color::Black, FLOODFILLBORDER); will not work.

Answer 3

Yes, floodfill shows that problem, but it is working with fractional starting points.

Below is almost all my code. The disputed part is right up front in the Form_Load proc. Which paints a ring on 2 3000x3000 twip pictureboxes. Pic1, the left, works for positioning(centered), origin location(center), and fills. Pic2 doesn’t work quite right. The ring displays at 2x the size (my earlier comment of 4x was wrong) , its origin is at the upperleft corner, and fill works. I tried both -100, -100 and 100, 100 for the Viewportorg statement. It seemed to have no effect.
.

Dim SideNum As Integer 'counts from 1 to sides as we go around ring

Private Sub Form_Load()
Me.Show

Pic1.ScaleMode = vbInches
size = 5
Pic1.ScaleWidth = size
Pic1.ScaleHeight = size
DrawRing Pic1, PointOf(2.5, 2.5), 12, 2, 1.5
fill Pic1, PointOf(2.5, 2.5), RGB(255, 255, 0)
fill Pic1, PointOf(-2.3, -2.3), RGB(0, 0, 255)

Pic2.ScaleMode = vbInches
SetMapMode Pic2.hDC, MM_ISOTROPIC
SetWindowExtEx Pic2.hDC, 1, 1, Null
SetViewportExtEx Pic2.hDC, GetDeviceCaps(Pic2.hDC, LOGPIXELSX), -GetDeviceCaps(Pic2.hDC,LOGPIXELSY), Null
SetViewportOrgEx hDC, -100, -100, Null
DrawRing Pic2, PointOf(0, 0), 12, 2, 1.5
fill Pic2, PointOf(0, 0), RGB(255, 255, 0)
End Sub

Private Sub DrawRing(dest As PictureBox, Origin As ObjPt, Sides As Integer, Radius As Single, Wall As Single)
Dim SO1 As ObjPt 'gap adjusted segment outer previous
Dim SO2 As ObjPt 'gap adjusted segment outer current
Dim SI1 As ObjPt 'gap adjusted segment inner previous
Dim SI2 As ObjPt 'gap adjusted segment inner current
Dim Ctr As ObjPt
Dim Angle As Single 'current Angle
Dim InitialAngle As Single 'first angle in loop to display ring
Dim Miter As Single
InitialAngle = 0
FinalAngle = 360
SideNum = 0
Miter = 180 / Max(Sides, 1) 'Get apparent Cutting Angle
While Angle <= FinalAngle 'loop around the circle to create segments
SideNum = SideNum + 1
PolarToCartesian Origin, Radius, Angle - 2 * Miter, SO1 'get X,Y of prior outer corner
PolarToCartesian Origin, Radius - Wall, Angle - 2 * Miter, SI1 'get X,Y of prior inner corner
PolarToCartesian Origin, Radius, Angle, SO2 'get X,Y of current outer corner
PolarToCartesian Origin, Radius - Wall, Angle, SI2 'get X,Y of current inner corner
DrawLineObj dest, "lft", SI1, SO1, 0 'first inter-segment boundary
DrawLineObj dest, "out", SO1, SO2, 0 'outer edge
DrawLineObj dest, "inr", SI1, SI2, 0 'inner edge
DrawLineObj dest, "rgt", SI2, SO2, 0 'final inter-segment boundary
CtrPoint SI1, SO1, SI2, SO2, Ctr
fill dest, Ctr, RGB(255 - 10 * SideNum, 0, 0)
Angle = Angle + 2 * Miter 'advance to next segment in the circle/riing
Wend
End Sub

Private Sub fill(dest As PictureBox, Ctr As ObjPt, Color As Long)
Dim p As ObjPt
Dim rtn As Long
dest.FillStyle = cSolid
dest.fillcolor = Color 'set fill style and color
ScaleToPixelsObj dest, Ctr, p
rtn = ExtFloodFill(dest.hDC, p.X, p.y, 0, FLOODFILLBORDER) 'do the fill
End Sub

Private Sub ScaleToPixelsObj(Pic As PictureBox, FromObj As ObjPt, ToObj As ObjPt)
With FromObj
ToObj.X = Pic.ScaleX(.X, Pic.ScaleMode, vbPixels)
ToObj.y = Pic.ScaleY(.y, Pic.ScaleMode, vbPixels)
End With
End Sub

Private Function PointOf(X As Single, y As Single) As ObjPt
Dim ans As ObjPt
ans.X = X
ans.y = y
PointOf = ans
End Function