Improving Image Display Performance

[Guest]

Hi,

In an application I have to display a video composed of several frames that
I capture from a camera embedded in a Pocket PC. For each captured frame, I
create a Bitmap object, and display it in a PictureBox.

I get around 15 frames per seconds in 160x120, which is quite good. But when
I looked in details, I could see that 75% of the computational costs are due
to the bitmap creation and bitmap display!... only 25% are due to the frame
capture, and frame treatments.

Do you think of any alternative way to improve image display performance ?
Frames are stored as an array of byte, (RGB16bit:565 format) what would be
the most efficient way to display them to the screen ?

Thanks a lot!

Lionel Reyero

Here is a piece of the code I used so far :


pictureBox.Image = CreateBitmap(width, height, bpp, false, frameBytes);

// Creates System.Drawing.Bitmap from raw 16- or 24-bit data provided
protected static Bitmap CreateBitmap(int width, int height, int bpp, bool
inverted, byte[] bits)
{
// Size of BITMAPFILEHEADER structure
const uint fileHeaderSize = 14;

// Size of BITMAPINFOHEADER structure
const uint bitmapInfoHeaderSize = 40;

// Size of bitmap bits
uint bitsSize = (uint)(((width * bpp + 3) & ~3) * height);

// Size of the entire BMP-file
uint bitmapSize = fileHeaderSize + bitmapInfoHeaderSize + bitsSize;

// Creating memory stream to place our BMP-file to
MemoryStream stream = new MemoryStream(new byte[bitmapSize]);
BinaryWriter writer = new BinaryWriter(stream);

// Writing BITMAPFILEHEADER
writer.Write((byte)'B');
writer.Write((byte)'M');
writer.Write(bitmapSize);
writer.Write((ushort)0);
writer.Write((ushort)0);
writer.Write(fileHeaderSize + bitmapInfoHeaderSize);

// Writing BITMAPINFOHEADER
writer.Write((uint)bitmapInfoHeaderSize);
writer.Write(width);
writer.Write(!inverted ? -height : height);
writer.Write((ushort)1);
writer.Write((ushort)(bpp * 8));
writer.Write((uint)(0));
writer.Write((uint)0);
writer.Write((int)0);
writer.Write((int)0);
writer.Write((uint)(0));
writer.Write((uint)0);

// Writing actual bitmap bits. We do not perform any alignment padding here
// because all preview and capture modes are typically aligned properly, i.e.
// have their width a multiple of 4
writer.Write(bits);

return new Bitmap(stream);
}

 

[Alex Feinman [MVP]]

The most efficient way would be probably using GAPI in 5:6:5 mode. You will
be able to copy blocks of bytes directly to video frame buffer.
Using GAPI might require copying gx.dll from SDK\Target\ARMv4 directory (if
it's not on the deivice).
P/Invoking GAPI functions is not exactly straightforward. You might find
some help here (code is kind of dirty, but you'll get the bits that you
need): http://www.alexfeinman.com/download.asp?doc=GAPITest.zip


--
Alex Feinman
---
Visit http://www.opennetcf.org

Hi,

In an application I have to display a video composed of several frames
that
I capture from a camera embedded in a Pocket PC. For each captured frame,
I
create a Bitmap object, and display it in a PictureBox.

I get around 15 frames per seconds in 160x120, which is quite good. But
when
I looked in details, I could see that 75% of the computational costs are
due
to the bitmap creation and bitmap display!... only 25% are due to the
frame
capture, and frame treatments.

Do you think of any alternative way to improve image display performance ?
Frames are stored as an array of byte, (RGB16bit:565 format) what would be
the most efficient way to display them to the screen ?

Thanks a lot!

Lionel Reyero

Here is a piece of the code I used so far :


pictureBox.Image = CreateBitmap(width, height, bpp, false, frameBytes);

// Creates System.Drawing.Bitmap from raw 16- or 24-bit data provided
protected static Bitmap CreateBitmap(int width, int height, int bpp, bool
inverted, byte[] bits)
{
// Size of BITMAPFILEHEADER structure
const uint fileHeaderSize = 14;

// Size of BITMAPINFOHEADER structure
const uint bitmapInfoHeaderSize = 40;

// Size of bitmap bits
uint bitsSize = (uint)(((width * bpp + 3) & ~3) * height);

// Size of the entire BMP-file
uint bitmapSize = fileHeaderSize + bitmapInfoHeaderSize + bitsSize;

// Creating memory stream to place our BMP-file to
MemoryStream stream = new MemoryStream(new byte[bitmapSize]);
BinaryWriter writer = new BinaryWriter(stream);

// Writing BITMAPFILEHEADER
writer.Write((byte)'B');
writer.Write((byte)'M');
writer.Write(bitmapSize);
writer.Write((ushort)0);
writer.Write((ushort)0);
writer.Write(fileHeaderSize + bitmapInfoHeaderSize);

// Writing BITMAPINFOHEADER
writer.Write((uint)bitmapInfoHeaderSize);
writer.Write(width);
writer.Write(!inverted ? -height : height);
writer.Write((ushort)1);
writer.Write((ushort)(bpp * 8));
writer.Write((uint)(0));
writer.Write((uint)0);
writer.Write((int)0);
writer.Write((int)0);
writer.Write((uint)(0));
writer.Write((uint)0);

// Writing actual bitmap bits. We do not perform any alignment padding
here
// because all preview and capture modes are typically aligned properly,
i.e.
// have their width a multiple of 4
writer.Write(bits);

return new Bitmap(stream);
}

 

[Guest]

Thanks Alex,
However, there is something wrong with your link, I.E. fails to open the link.

Lionel

 

[Alex Feinman [MVP]]

Sorry, sometimes file permissions on my server get screwed. Should be ok
now.