image filtering advanced
DESCRIPTION
Image Filtering Advanced. Image filtering with GDI and DX HW accelerations. An introduction : domain terms. Bitmap (let’s assume Bitmap == GDI+ Bitmap) System memory portion containing Pixel as color’s byte DX Surface System or Video memory portion representing a bitmap Texture - PowerPoint PPT PresentationTRANSCRIPT
Image Filtering Advanced
Image filtering with GDI and DX HW accelerations
Image Filtering Advanced
An introduction : domain terms
♦ Bitmap (let’s assume Bitmap == GDI+ Bitmap)System memory portion containing Pixel as color’s byte
♦ DX SurfaceSystem or Video memory portion representing a bitmap
♦ TextureMainly Video memory portion containing a bitmap that
will be mapped onto a polygon
Image Filtering Advanced
Enhanced Image Filter Library
♦ What does a filter do?♦ What is a filter?♦ What is a filter chain?
A filter is a function from image to image,A filter chain is a functional composition so,
it’s a function again.
Image Filtering Advanced
The speed part 1 : unsafeprotected override void filter(Bitmap b, Bitmap[] temp) {
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0;
unsafe {byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;int nWidth = b.Width * 3;
for(int y=0;y<b.Height;++y) { for(int x=0; x < nWidth; ++x ) {
p[0] = (byte)(255-p[0]);++p;
} p += nOffset;}
} b.UnlockBits(bmData);}
}
This way is faster than accessing pixels through the GetPixel GDI function
Image Filtering Advanced
Filter
Brightness
ColorCorrector
Contrast
Conv3x3
EdgeDetectConvolution EdgeDetectDifference
EdgeDetectHomogenity
EdgeDetectHorizontal
EdgeDetectQuick
EdgeDetectVertical
EdgeEnhance EmbossLaplacian
Gamma
GaussianBlur
GrayScale
Invert
MeanRemoval
Sharpen
Smooth
Library structure
Image Filtering Advanced
The key for success : the filter base class design
[Serializable] public abstract class Filter {
private Filter next;protected Filter(Filter f) { next = f;}protected Filter() { next = null;}protected abstract void filter(Bitmap b, Bitmap[] temp);
protected abstract int NumCopies { get; }
public BaseConf GetConfig(){ return new BaseConf();}
public void Apply(Bitmap b) { int n = this.NumCopies; Filter p = next; while (p != null) {
n = Math.Max(n, p.NumCopies);p = p.next;
} Bitmap[] tmp = new Bitmap[n]; for (int i = 0; i < n; i++)
tmp[i] = new Bitmap(b.Width, b.Height); p = this; do {
p.filter(b, tmp);p = p.next;
} while (p != null); foreach (Bitmap bm in tmp) {
bm.Dispose(); }}
}
Create all the temporaryImages before your filterchain goes with its work!
Image Filtering Advanced
The speed part 2 : ngen♦ Let’s get native!Run the ngen tool on the filter library
assembly to get it compiled once for all.
Image Filtering Advanced
♦ A little trick to achieve the real magic♦ Let’s pretend :
♦ Remember you gain speed but you get also limitations!
Image => plane => polygon
The speed part 3 : Get HW!
Image Filtering Advanced
DX Structure♦ We can use the HW
3D acceleration to boost 2D image filtering using the Programmable Pixel Shader
Image Filtering Advanced
HSL with DX 9♦ Cross Hardware language!♦ Can contains multiple techniques and
passes!♦ Exposes a large number of common
function as lerp and so on
Image Filtering Advanced
HSL Stupid Examplefloat4 Light(float3 LightDir : TEXCOORD1, uniform
float4 LightColor, float2 texcrd : TEXCOORD0, uniform sampler samp) : COLOR
{ float3 Normal = tex2D(samp,texcrd); return dot((Normal*2 - 1), LightDir)*LightColor;
}
Image Filtering Advanced
The Idea1. Create a DX device on a control2. Create a 3D plane3. Put the image you want to process on
the plane as a texture4. Use the Pixel Shader Program to make
the GPU works for you5. Use the Control Graphics class to save
your processed image.
Image Filtering Advanced
A simple but real FX example
Image Filtering Advanced
And the cons?Here we are . . .♦ You can use only power of 2 sized bitmap♦ The display size is the maximum size for
the output image. . . But you get a common PC running as it’s
got a real expensive (and dedicated) DSP!
Image Filtering Advanced
The Direct Show way♦ DShow use a graph from sources to
renderes (audio and video)♦ Along the graph you can have filters♦ 2 approaches
– In place transformations– Not in place transformations
♦ Only C++ (the unmanaged one!)
Image Filtering Advanced
CTransformFilter::Transform
♦ This filter uses the CTransformInputPin class for its input pin, and the CTransformOutputPin class for its output pin.
♦ Use this base class if you want to try filter and then pass it through the graph
♦ Beware of memory leak!
Image Filtering Advanced
Example of transformHRESULT CRleFilter::Transform(IMediaSample *pSource, IMediaSample *pDest) {
// Get pointers to the underlying buffers. BYTE *pBufferIn, *pBufferOut; hr = pSource->GetPointer(&pBufferIn); if (FAILED(hr)) {
return hr; } hr = pDest->GetPointer(&pBufferOut); if (FAILED(hr)) {
return hr; } // Process the data. DWORD cbDest = EncodeFrame(pBufferIn, pBufferOut); KASSERT((long)cbDest <= pDest->GetSize()); pDest->SetActualDataLength(cbDest); pDest->SetSyncPoint(TRUE); return S_OK;
}
Image Filtering Advanced
CTransInPlaceFilter::Transform
♦ Transform the input sample in place♦ Use it for real real-time processing♦ What do you want more?
Image Filtering Advanced
The Frame Dispatcer ClassIf you want to apply filter to a real time
camera or to an avi file in C# there’s an utility from the Medialab (university of Pisa) that can help you to get your frames inside a managed application!
Image Filtering Advanced
References♦ Enhanced Filter Library and Frame
Dispatcer– http://dotnet.di.unipi.it