Android Question get data YCbCr_420_SP format from Camera1_Preview

joop · Jan 18, 2016

Hi, I want to get data in YCbCr_420_SP format from the Camera1_Preview event like this :

B4X:

Sub Camera1_Preview (PreviewPic() As Byte)
    If DateTime.Now > lastPreviewSaved + IntervalMs Then
        Dim in As InputStream
        Dim bmp As Bitmap
        in.InitializeFromBytesArray(PreviewPic, 0, PreviewPic.Length)
        Log("Length PrevPicArr=" & PreviewPic.length)
        Log(PreviewPic(2000)) ' is there something in the array ?
        Try
         bmp.Initialize2(in)
         ImageView1.Bitmap = bmp
         Panel2.setbackgroundimage(bmp)
        Catch
        Log("catch " & LastException)
        End Try
        lastPreviewSaved =DateTime.Now
    End If
End Sub

the line bmp.Initialize2(in)" line gives this error in the catch .
java.lang.RuntimeException: Error loading bitmap. Sub

I read this link about this problem,but with try and catch I can't make it work.
https://www.b4x.com/android/forum/t...late-the-camera-preview-frames.20073/#content.

There are negative and positive values in the stream array is this the problem.?
Can a Bitmap be filled with YCbCr format.? bmp.Initialize2(in)

JordiCP · Jan 18, 2016

You need to convert the preview data to a different format first. There are different ways to do it.

Try THIS for one of these methods

joop said:
There are negative and positive values in the stream array is this the problem.?
Can a Bitmap be filled with YCbCr format.? bmp.Initialize2(in)

About your 2 last questions, the negative values aren't so in origin. But as the array holds 8-bit data and the only 8-bit basic type in android is (signed)byte, when you look at their value, they are signed. Better think of them as values ranging from 0x00 to 0xFF
A bitmap needs RGBA888 values when initialized in B4A. You could also used RGB565 with inline java or using existing libraries, but no NV21 YCbCr format

joop · Jan 18, 2016

Thanks Jordi,! I understand now , I 'll try your library to convert YCbCr_420_SP to RGBA888
and initialize the bitmap.

joop · Jan 25, 2016

hi Jordi , i used your lib to changed the brightness ( Y luma) for a bitmap.
using the first 307200 bytes.

with this parameters :

camera is always in landscape
myBitmap.Width myBitmap.Height = 640 480
camEx.PreviewHeight camEx.PreviewWidth = 480 640
camEx rotation = 90
this works ok ! .

My camera has these resolutions

Cam Size: 2560x1920
Cam Size: 2560x1536
Cam Size: 2048x1536
Cam Size: 2048x1232
Cam Size: 1600x1200
Cam Size: 1600x960
Cam Size: 800x480
Cam Size: 640x480

How can I change the PreviewHeight en PreviewWidth to a higher resolution en display a
part of this image to the bitmap. (2560x1920)?

JordiCP · Jan 25, 2016

Are these resolutions preview resolutions or picture resolutions? (the camera gives you both)

Not sure to understand correctly your question:

> Do you mean that you want to work with the maximum preview resolution, only process a part of the preview data and then convert this part into a bitmap to show it on screen?

> If so, is it always the same "rectangle" and always the same operation or it can vary dinamically?

joop · Jan 25, 2016

This the show preview routine Sizes

B4X:

Dim csz() As CameraSize

    csz = camEx.GetSupportedPreviewSizes

    For Each cs As CameraSize In csz
      Log("Cam Size: " & cs.Width & "x" & cs.Height)
    Next

Yes that's what I mean , it is always displayed in a rectangle bitmap.
this bitmap has always the same size.

Maybe this isn't possible now I think about it again .

JordiCP · Jan 26, 2016

If what you want is that the bitmap fits the whole screen, just change in the example (in Activity_Create)

B4X:

    'Activity.AddView(myIV,50%X,50%Y,50%X,50%Y) '<-- Comment this line 
    Activity.AddView(myIV,0,0,100%X,100%Y)'50%X,50%Y,50%X,50%Y) '<-- This line instead of the above

The bitmap will be the same but the system will scale it for you (you will see that if you choose scale=1, the quality is good enough. Also, if you must process the preview t is not a good idea to work with very high resolutions)

joop · Jan 26, 2016

Thanks, I will try that.

Android Question get data YCbCr_420_SP format from Camera1_Preview

joop

Active Member

JordiCP

Expert

joop

Active Member

joop

Active Member

JordiCP

Expert

joop

Active Member

JordiCP

Expert

joop

Active Member

Similar Threads

Android Question get data YCbCr_420_SP format from Camera1_Preview

Active Member

Expert

Active Member

Active Member

Expert

Active Member

Expert

Active Member

Similar Threads

Privacy & Transparency

Privacy & Transparency