Android Question How do I get ABExtDrawing drawBitmap4 to only draw what is inside the source coordinates

[NeoTechni]

When I use ABExtDrawing drawBitmap4, it draws the entire source image, instead of what's inside the source coordinates. I've been using a clip path to stop it from drawing the rest, but the larger the image is, the slower this method is. What is the proper way to draw an image as a polygon?

'SRC and DEST are an array of X-then-Y coordinates in the same direction (ie: clockwise)
Sub DrawBMPpoly(BG As Canvas, BMP As Bitmap, SRC() As Float, DEST() As Float, Alpha As Int, NeedsClipPath As Boolean)
   Dim temp As Int, P As Path
   If SRC.Length = DEST.Length Then
       ExDraw.save2(BG, ExDraw.MATRIX_SAVE_FLAG)
       mPaint.Initialize
       mPaint.SetAlpha(Alpha)
       mMatrix.setPolyToPoly(SRC, 0, DEST, 0, DEST.Length *0.5)
       If NeedsClipPath Then
           P.Initialize(DEST(0),DEST(1))
           For temp = 2 To DEST.Length -1 Step 2
               P.LineTo(DEST(temp),DEST(temp+1))
           Next
           BG.ClipPath(P)
       End If
       ExDraw.drawBitmap4(BG, BMP,  mMatrix, mPaint)
       ExDraw.restore(BG) 'before Activity.Invalidate
       If NeedsClipPath Then BG.RemoveClip
   End If
End Sub

 

[Erel]

You can use BitmapCreatorEffects draw through mask feature:

https://www.b4x.com/android/forum/threads/b4x-bitmapcreator-effects.93608/#content

I don't think that it will be faster than clipping the path. The main advantage is that you can easily create complex shapes.

 

[NeoTechni]

I've actually been looking for that too. But it wouldn't apply in this scenario. I use DrawPoly mainly to fake 3D effects, like drawing a square texture as a parallelogram to make it seem like it's falling and such. But DrawPoly wants to draw the entire texture (which is huge) instead of just the part in the source coordinates... The drawing of the entire texture is what's slowing it down

 

[Erel]

In many cases you can improve the drawing performance by scaling down the canvas. Most devices scale is 2+ so the canvas size can be very large. The visual difference can be minimal.