Wish DrawBitmap no source rectangle

Discussion in 'iOS Bugs & Wishlist' started by klaus, Nov 18, 2014.

  1. klaus

    klaus Expert Licensed User

    In B4A the DrawBitmap method has a SourceRectangle parameter to draw a part of the source bitmap.
    In B4i the SourceRectangle parameter is missing.
    Same for DrawBitmapRotated.
    Is this an iOS limitation ?
  2. Erel

    Erel Administrator Staff Member Licensed User

    There is no native API for this like in Android. However you can use these two methods to implement it:
    Sub DrawBitmapRotated(canvas1 As Canvas, Bitmap1 As Bitmap, SrcRect As Rect, DestRect As Rect, Degrees As Float)
    Dim no As NativeObject = canvas1
    "rotate:::"Array(Degrees, DestRect.CenterX, DestRect.CenterY))
       DrawBitmap(canvas1, Bitmap1, SrcRect, DestRect)
    "rotate:::"Array(-Degrees, DestRect.CenterX, DestRect.CenterY))
    End Sub

    Sub DrawBitmap(canvas1 As Canvas, Bitmap1 As Bitmap, SrcRect As Rect, DestRect As Rect)
    If SrcRect = Null Then
    Dim SrcRect As Rect
    00, Bitmap1.Width, Bitmap1.Height)
    End If
    Dim p1 As Path
    Dim sx, sy As Float
       sx = (DestRect.Right - DestRect.Left) / (SrcRect.Right - SrcRect.Left)
       sy = (DestRect.Bottom - DestRect.Top) / (SrcRect.Bottom - SrcRect.Top)
    Dim x, y, width, height As Int
       x = DestRect.Left - sx * SrcRect.Left
       y = DestRect.Top - sy * SrcRect.Top
       width = Bitmap1.Width * sx
       height = Bitmap1.Height * sy
    Dim d2 As Rect
       d2.Initialize(x, y, x + width, y + height)
       canvas1.DrawBitmap(Bitmap1, d2)
    End Sub
    They behave like B4A DrawBitmap and DrawBitmapRotated.
  3. sorex

    sorex Expert Licensed User

    I don't want to sound harsh but...

    isn't it the purpose of B4x to stick to the same common methods/syntax in all tools to make it easier for us switching between B4A/B4i/B4J?

    why wasn't it added to the core like this in the first place so that our copy paste of code would've worked?

    don't feel offended but i'm getting into one surprise after the other while expecting it to be more simular.
  4. Erel

    Erel Administrator Staff Member Licensed User

    It is one of the purposes. However when the native APIs are too different there is always a tension between building a thick abstraction above the native APIs vs. a thin abstraction. There is a price for thick abstractions.

    As you can see in the above code, creating a DrawBitmap method that is identical to B4A DrawBitmap method requires quite a lot of "heavy" work (atruntime). In this case I decided to follow the native API which I believe provides the feature required in 95%+ of the cases (where you want to draw the full bitmap). In the other cases you can use the code I posted here.
    thedesolatesoul likes this.
  5. Erel

    Erel Administrator Staff Member Licensed User

    Not offended. iOS and Android are very different platforms. As someone who is deeply familiar with both platforms I'm very happy with the amount of code that can be reused between the platforms. More importantly, B4i follows the same concepts of B4A and B4J which means that it should not be too difficult for a developer to switch from one platform to another.
    ilan, Mark Turney, iCAB and 2 others like this.
  6. sorex

    sorex Expert Licensed User

    I will put a thread in the tutorials section about the changes I went through for a simple game I ported from B4A > B4i.

    It might be handy reference for some people.

    It just took an evening which is still faster than writing it from scratch.
    Erel likes this.
  7. iCAB

    iCAB Well-Known Member Licensed User

    Hi Guys

    I am trying to achieve the exact same result in B4I for the code below

    Sub RotateImage(original As Bitmap, degree As Float) As Bitmap
    Dim matrix As JavaObject
    Dim bmp As JavaObject
    Dim NewImage As Bitmap = bmp.RunMethod("createBitmap"Array(original, 00, original.Width, original.Height, _
    Return NewImage
    End Sub

    I would to be able to save the returned image.

    Thank you
  8. Erel

    Erel Administrator Staff Member Licensed User

    Please start a new thread for this in the questions forum.
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