Crash in app
lazarus / 43-Android

----------------------------------------------------------------------
biologic · 2025-03-23 03:11

Maybe someone more experienced in LAMW can help.

Many thanks.

----------------------------------------------------------------------
biologic · 2025-03-23 16:59

The code I want to make is :

- Open a bitmap with a press on a button (done)
- Show rhe bitmap on the form (done)
- with a press on 'convert' button, change the pixels to grayscale of
the opened bitmap,
and show the changed bitmap on the form.
- with a press on the 'save' button, save this new gray bitmap.

I'm stuck in step 3, convert bitmap to grayscale.

----------------------------------------------------------------------
biologic · 2025-03-28 22:49

I Found a good resource on Bitmaps in one of the AppDrawingInBitmap
examples.

https://en.proft.me/2017/08/2/how-work-bitmap-android/

----------------------------------------------------------------------
biologic · 2025-03-30 17:21

Anyone knows how to read/write a pixel from a jBitmap/jCanvas ?

----------------------------------------------------------------------
dseligo · 2025-03-31 08:37

I don't have time to test it now, but ...

Try to use BitmapToArrayOfJByte method, something like:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var  posX,
posY, bitmapWidth, bitmapHeight, bytesByLine: Word;  red, green, blue:
Integer;  ABmp: jBitmap;  baBmp: TDynArrayOfJByte;  iNumPixels:
Integer;begin  ... // load image to ABmp  ...  bitmapWidth :=
ABmp.GetWidth();  bitmapHeight := ABmp.GetHeight();  bytesByLine :=
Ceil(bitmapWidth / 8);  baBmp := nil;  iNumPixels :=
ABmp.BitmapToArrayOfJByte(baBmp); // to array in RGBA format   for
posY := 0 to bitmapHeight - 1 do // for every row  begin    While j <
bitmapWidth do // for every column    begin      For k := 0 to 7 do //
for every bit bit in column byte      begin        posX := j + k;    
  if posX < bitmapWidth then // it doesn't have to be whole byte at
last column        begin          // RGB values, I don't need alpha
channel (alpha channel is +3)          red   := Byte(baBmp[ posY *
bitmapWidth * 4 + posX * 4 + 0 ]);          green := Byte(baBmp[ posY
* bitmapWidth * 4 + posX * 4 + 1 ]);          blue  := Byte(baBmp[
posY * bitmapWidth * 4 + posX * 4 + 2 ]);          ...          // you
can do something now with pixel RGB values        end;      end;     
j := j + 8;    end;  end;  ...  // convert it to new bitmapend;
I didn't convert back to bitmap, because I am printing to POS printer.
I see that methods GetBitmapFromJByteArray and SetByteArrayToBitmap
exists, probably you can use them to get bitmap back from byte array.

----------------------------------------------------------------------
biologic · 2025-03-31 12:52

Thank you. 

I will try this as soon as I can.
Next weekend probably.

----------------------------------------------------------------------
biologic · 2025-04-06 18:03

If I want to call the getPixels method of the Bitmap Java object,
can this be done inside the project code ?

Or

Something different to do ?

Thanks

----------------------------------------------------------------------
biologic · 2025-04-09 07:57

I found a good explanation at Chatgpt.