magnify

[jake]

magnify a section of bitmap

I have an image 2816x2112(4:3) that I'm setting as activity background using loadBitmapSample with max width=activity.width(800) and max height=activity.height(1205) with the drawable gravity.center.

I'm wanting to magnify an area of the background by using a small source
rectangle with a destination rectangle of larger size. To do
this magnification I'm using: canvas.drawbitmap(bitmap,source rectangle,destination rectangle)

My issue is that the canvas image is not of the area outlined by the source rectangle(outlined in black by cvs.drawlines), but is instead displaying an area off to the left of the source rectangle.

I'm running on a Nexus 7, and haven't been able to figure this out.

Sub Process_Globals    

End Sub
Sub Globals

End Sub
Sub Activity_Create(FirstTime As Boolean)    

   If File.Exists (File.DirRootExternal, "sp_1149.jpg") = False OR File.Size(File.DirRootExternal, "sp_1149.jpg")=0 Then   
      File.Copy(File.DirAssets, "sp_1149.jpg", File.DirRootExternal, "sp_1149.jpg") 
   End If

   Activity.LoadLayout("test")

   Dim strFile,strDir As String
   strFile="sp_1149.jpg"
   strDir=File.DirRootExternal
   Dim d As BitmapDrawable
   d.Initialize(LoadBitmapSample(strDir,strFile,Activity.Width,Activity.Height))
   d.Gravity=Gravity.CENTER
   Activity.Background=d

   Dim cvs As Canvas
   cvs.Initialize(Activity)
   
   Dim sRect As Rect
   sRect.Initialize(55%x,45%y,60%x,50%y)
   
    Dim dRect As Rect
    dRect.Initialize(40%x,60%y,70%x,90%y)
    
    cvs.DrawBitmap(LoadBitmapSample(strDir,strFile,Activity.Width,Activity.Height),sRect,dRect)
    cvs.drawline(sRect.left,sRect.Top,sRect.Left,sRect.Bottom,Colors.Black,3dip)
    cvs.drawline(sRect.left,sRect.Bottom,sRect.Right,sRect.Bottom,Colors.Black,3dip)
    cvs.drawline(sRect.right,sRect.Bottom,sRect.Right,sRect.top,Colors.Black,3dip)
    cvs.drawline(sRect.right,sRect.top,sRect.Left,sRect.top,Colors.Black,3dip)

End Sub

 

[Erel]

Why do you load the bitmap twice?

The problem is that LoadBitmapSample returns an image equal or larger than the specified size. You can check the return size with Bitmap.Width / Height.

Another option is to use this library to only load the requires size: Jpeg library

 

[jake]

magnify a section of bitmap

The first load is the background image, and the canvas image is the foreground magnified image(destination rectangle).

The difficulty is in understanding the relation between the source rectangle parameters and the displayed background. If I set the source rectangle left and top as 0,0. What I end up with in my destination rectangle is not what is visible in the upper left corner of the image on my device.

 

[Erel]

The first load is the background image, and the canvas image is the foreground magnified image(destination rectangle).

You can still load it once to a Bitmap object.

If I set the source rectangle left and top as 0,0. What I end up with in my destination rectangle is not what is visible in the upper left corner of the image on my device.

It should be. Can you upload your project?