In FireMonkey, Bitmap is the common currency for working with images. If you want to send an image via Stream using LiveBindings or want to save an Image to disk or into a database on a device with limited storage however, they are quite large.
Thankfully FireMonkey has a really easy to use CodecManager that allows you to SaveToFile or SaveToStream and convert to PNG or JPG across all platforms (which are vastly smaller in size).
Creating a PNG, JPG/JPEG is as simple as calling the Bitmap.SaveToFile with the correct file extension. This works really well with even more extensions supported.
Personally I would use PNG as the JPG formats are around the same size on some test I’ve run, but produce a better quality of image, especially when grabbing screenshots.
SaveToStream and TBitmapCodecManager
Bitmap.SaveToStream doesn’t expose the CodexManager in the same way as it is available automatically with the SaveToFile option so takes a little more work to get a compressed image into the memory stream.
This is done using the TBitmapCodecManager class. A simple screen test has gone from over 1mb as a bitmap to around 6kb when saved to PNG using this approach.
The following code is an example using two image viewers (and a few save to files to help demonstrate the difference in file size). The key part is the TBitmapSurface and TBitmapCodecManager.
procedure TForm1.Button1Click(Sender: TObject); var Stream: TMemoryStream; Surf: TBitmapSurface; aFile : string; begin ImageViewer1.Bitmap := TabControl1.MakeScreenshot; // Comparison save file as BMP aFile := 'c:\test\myImage'; ImageViewer1.Bitmap.SaveToFile(aFile+'.bmp'); Stream := TMemoryStream.Create; try Stream.Position := 0; Surf := TBitmapSurface.Create; try Surf.Assign(ImageViewer1.Bitmap); // use the codec to save Surface to stream if not TBitmapCodecManager.SaveToStream( Stream, Surf, '.png') then raise EBitmapSavingFailed.Create( 'Error saving Bitmap to png'); finally Surf.Free; end; // do something with the png stream image Stream.Position := 0; ImageViewer2.Bitmap.LoadFromStream(Stream); // comparison output as PNG from the stream Stream.Position := 0; Stream.SaveToFile(aFile+'.png'); finally Stream.Free; end; end;
Now, you can obviously save as a ‘PNG’ from the bitmap, but the above code shows how to avoid saving a file to disk unless you really need to.