How to change bitmap from VCL.Graphics.TBitmap to FMX.Graphics.TBitmap - delphi

Question

I'm trying to show an image taken with a camera on a multi-device form with paintbox after processing it with opencv. However, cvImage2Bitmap returns VCL.Graphics.TBitmap. So I need to convert this to FMX.Graphics.TBitmap.
unit xml_cam2;
interface
uses
System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, VCL.Graphics, FMX.Dialogs, FMX.ScrollBox,
FMX.Memo, FMX.Objects, FMX.Controls.Presentation, FMX.StdCtrls,
ocv.highgui_c,
ocv.core_c,
ocv.core.types_c,
ocv.imgproc_c,
ocv.imgproc.types_c,
ocv.utils;
type
TForm1 = class(TForm)
Button1: TButton;
OpenDialog1: TOpenDialog;
PaintBox1: TPaintBox;
Memo1: TMemo;
procedure PaintBox1Paint(Sender: TObject; Canvas: TCanvas);
procedure FormCreate(Sender: TObject);
private
capture: pCvCapture;
frame: pIplImage;
procedure OnIdle(Sender: TObject; var Done: Boolean);
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
var
Bitmap, PaintBoxBitmap: FMX.Graphics.TBitmap;
{$R *.fmx}
procedure TForm1.FormCreate(Sender: TObject);
begin
capture := cvCreateCameraCapture(CV_CAP_ANY);
if Assigned(capture) then
Application.OnIdle := OnIdle;
end;
procedure TForm1.OnIdle(Sender: TObject; var Done: Boolean);
begin
if Assigned(capture) then
begin
frame := cvQueryFrame(capture);
if Assigned(frame) then
begin
Bitmap := cvImage2Bitmap(frame);
//cvImage2Bitmap returns VCL.Graphics.TBitmap
end;
end;
Memo1.Lines.Add(IntToStr(Bitmap.Width));
Memo1.Lines.Add(IntToStr(Bitmap.Height));
if (PaintBoxBitmap = nil) then
PaintBoxBitmap := FMX.Graphics.TBitmap.Create;
PaintBoxBitmap.Assign(Bitmap);
Invalidate;
Bitmap.Free;
end;
procedure TForm1.PaintBox1Paint(Sender: TObject; Canvas: TCanvas);
begin
if Assigned(PaintBoxBitmap) then
PaintBox1.Canvas.DrawBitmap(PaintBoxBitmap, PaintBox1.ClipRect, PaintBox1.ClipRect, 1);
Memo1.Lines.Add('b');
end;
end.
If you know any other efficient way to show iplimage to paintbox, please let us know.

Answer 1

It would be nice to move image data directly from one bitmap to the other, but doesn't seems to be an easy task.
Instead, the simplest way ( as it was answered here VCL.Bitmap To FMX.Bitmap ) seems to be to save image to a memory stream and load again in FMX bitmap object.
This simple code just works. You pay the penalty for moving image data to memory to load again in the new bitmap, but seems fair in exchange for simplicity.
procedure TForm1.FormCreate(Sender: TObject);
var
ms : TMemoryStream;
begin
ms := TMemoryStream.Create;
try
VCL_bmp := VCL.Graphics.TBitmap.Create;
try
VCL_bmp.LoadFromFile('file.bmp');
VCL_bmp.SaveToStream(ms);
ms.Seek(0, soFromBeginning);
finally
FreeAndNil(VCL_bmp);
end;
FMX_bmp := FMX.Graphics.TBitmap.Create();
try
FMX_bmp.LoadFromStream(ms);
... do something with the image ...
finally
FreeAndNil(FMX_bmp);
end;
finally
FreeAndNil(ms);
end;
end;

Answer 2

There are a couple of ways to do this. One way is to write the VCL bitmap to a TStream and then read it into the FMX bitmap. However, you can't convert the other way like that and it may be quite slow. I prefer to use Scanlines to convert between one and the other. In my code below I'm using 24 bit VCL bitmaps because I've found that the Windows API prefers these (AVIFile32 for example). Both bitmaps need to be created before calling the procedures. Of course you need to be creating an FMX application for Windows and include VCL.Graphics in your uses. Any transparency in the FMX bitmap will be lost when converting to a 24 bit VCL bitmap.
Convert 24 bit VCL bitmap to FMX bitmap
procedure VCLtoFMX_Bitmap(const VCLBmp : VCL.Graphics.TBitmap ; out FMXBmp : FMX.Graphics.TBitmap);
var
bData : TBitmapData;
x, y : Integer;
pfmxbyte, pvclbyte : PByte;
begin
VCLBmp.PixelFormat := pf24bit;
FMXBmp.SetSize(VCLBmp.Width, VCLBmp.Height);
FMXBmp.Map(TMapAccess.ReadWrite, bdata);
try
for y := 0 to FMXBmp.Height - 1 do begin
pfmxbyte := bdata.GetScanline(y);
pvclbyte := VCLBmp.Scanline[y];
for x := 0 to FMXBmp.Width - 1 do begin
pfmxbyte^ := pvclbyte^; Inc(pvclbyte); Inc(pfmxbyte);
pfmxbyte^ := pvclbyte^; Inc(pvclbyte); Inc(pfmxbyte);
pfmxbyte^ := pvclbyte^; Inc(pvclbyte); Inc(pfmxbyte);
pfmxbyte^ := $FF; Inc(pfmxbyte); // Full opacity
end;
end;
finally
FMXBmp.Unmap(bdata);
end;
end;
Convert FMX bitmap to 24 bit VCL bitmap
procedure FMXtoVCL_Bitmap(const FMXBmp : FMX.Graphics.TBitmap ; out VCLBmp : VCL.Graphics.TBitmap);
var
bData : TBitmapData;
x, y : Integer;
pfmxbyte, pvclbyte : PByte;
begin
VCLBmp.PixelFormat := pf24bit;
VCLBmp.SetSize(FMXBmp.Width, FMXBmp.Height);
FMXBmp.Map(TMapAccess.Read, bdata);
try
for y := 0 to FMXBmp.Height - 1 do begin
pfmxbyte := bdata.GetScanline(y);
pvclbyte := VCLBmp.Scanline[y];
for x := 0 to FMXBmp.Width - 1 do begin
pvclbyte^ := pfmxbyte^; Inc(pvclbyte); Inc(pfmxbyte);
pvclbyte^ := pfmxbyte^; Inc(pvclbyte); Inc(pfmxbyte);
pvclbyte^ := pfmxbyte^; Inc(pvclbyte); Inc(pfmxbyte, 2);
end;
end;
finally
FMXBmp.Unmap(bdata);
end;
end;