iOS Question Mass extraction of a bitmap's pixels

[JackKirk]

In B4A I can do a mass extraction of a bitmap's pixels by:

Dim pixels(bmp.Width * bmp.Height) As Int
Dim jo = bmp As JavaObject
jo.RunMethod("getPixels", Array As Object(pixels, 0, bmp.Width, 0, 0, bmp.Width, bmp.Height))

Which seems to be incredibly efficient.

In B4I I have been looking all over the forums for the last 6 hours, experimented with iRandomAccessFile etc - all to no avail - the only thing I have been able to find is JanPRO's Objective C pixel-by-pixel solution:

https://www.b4x.com/android/forum/threads/getpixelcolor.56922/#post-400769

which is as slow as a wet week if you do the obvious and put it inside a double set of For/Next.

Is there any efficient way to do this?

Thanks in anticipation...

 

[Erel]

See this thread: https://www.b4x.com/android/forum/t...iewdata-camera-in-an-array.63302/#post-401160

 

[JackKirk]

Thanks Erel,

I can now convert the bitmap to bytes and am then using ByteConverter.IntsFromBytes from the iRandomAccessFile library to extract pixels en mass, but this seems slow compared to the B4A solution in my first post - is there a faster way to extract Int from Byte?

Regards...

 

[Erel]

Why do you need to convert the pixels to int?

 

[JackKirk]

Erel,

I want to extract the pixels from the bitmap so I can analyse their colors.

Is there an alternate way to do this?

Regards...

 

[Erel]

If I remember correctly the bytes array returned stores each pixel as four bytes. You can access the bytes to get the pixel colors (RGB and alpha).

 

[JackKirk]

Erel,

OK, I did that and it is faster by a factor of about 2.

In LLCamera, is there anyway to get the preview data as YUV?

I don't mean take the supplied bitmap and reconstruct - I mean get the original YUV.

Thanks...

 

[Erel]

It is not possible.