Re: Converting Color to B&W

[Lieven <lieven quasar3d nl>]

On Mon, 17 Jul 2006 11:31:02 +0200, Petr Hracek <petr hracek siemens com>  
wrote:

Hi,

> 0.3*cPixelOriginal[y*width+x]+0.59*cPixelOriginal[y*width+x]+0.11*cPixelOriginal[y*width+x]
>           cPixelNew[y*width+x]=bw;

You aren't indexing your colour channels correctly. It should be

bw = 0.3*cPixelOriginal[(y*width+x) * 3]+0.59*cPixelOriginal[(y*width+x) *  
3 + 1]+0.11*cPixelOriginal[(y*width+x) * 3 + 2];

you should also store it in all 3 channels

cPixelNew[(y*width+x) * 3]=bw;
cPixelNew[(y*width+x) * 3 + 1]=bw;
cPixelNew[*y*width+x) * 3 + 2]=bw;

Greets,

Lieven van der Heide

> For converting from Color to B&W I used folowing technics, but
> unfortunatelly it does not work.
>
> //                           PixBuf
> cPixelOriginal = pbPixbufOriginal->get_Pixels();
> cPixelNew = (unsigned char *) malloc (width*height*sizeof(unsigned  
> char));
> rowstride = width *1; //for BW
> int bw;
>
> for(int y=0;y<height;y++)
> {
>     for(int x=0;x<width;x++)
>     {
>           ///                  red
>    green                                                blue
>           bw =
> 0.3*cPixelOriginal[y*width+x]+0.59*cPixelOriginal[y*width+x]+0.11*cPixelOriginal[y*width+x]
>           cPixelNew[y*width+x]=bw;
>     }
> }
> pbPixelNew=Gdk::Pixbuf::create_from_data(cPixelNew,Gdk::COLORSPACE_RGB,false,8,width,heigh,rowstride);
> But unfortunatelly it does not work.
>
> for display image I used method Gtk::Image image2;  
> image2.set(pbPixelNew);
>
> regards



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