Anonymní profil peter – Programujte.com

 To je ta druha funkce, ktera pouziva prave tu get_pixel. Radeji to sem dam, aby bylo jasnejsi, jak jsou ulozena data v tom obrazku. Pocet comps=3. Takze to nacita data, podle mne, jako RGBRGB... (0,3,6,... az do sirka*vyska orbrazku). Ale mozna, ze to chapu spatne :)

// Compute image error metrics.
static void image_compare(image_compare_results *pResults, int width, int height, const uint8 *pComp_image, int comp_image_comps, const uint8 *pUncomp_image_data, int uncomp_comps, int luma_only)
{
   double hist[256];
   double sum = 0.0f, sum2 = 0.0f;
   double total_values;
   const uint first_channel = 0, num_channels = 3;
   int x, y;
   uint i;

   memset(hist, 0, sizeof(hist));
   
   for (y = 0; y < height; y++)
   {
      for (x = 0; x < width; x++)
      {
         uint c;
         int a[3]; 
         int b[3]; 

         get_pixel(a, pComp_image + (y * width + x) * comp_image_comps, luma_only, comp_image_comps);
         get_pixel(b, pUncomp_image_data + (y * width + x) * uncomp_comps, luma_only, uncomp_comps);

         for (c = 0; c < num_channels; c++)
            hist[labs(a[first_channel + c] - b[first_channel + c])]++;
      }
   }

   pResults->max_err = 0;
   
   for (i = 0; i < 256; i++)
   {
      double x;
      if (!hist[i])
         continue;
      if (i > pResults->max_err)
         pResults->max_err = i;
      x = i * hist[i];
      sum += x;
      sum2 += i * x;
   }

   // See http://bmrc.berkeley.edu/…nt/psnr.html
   total_values = width * height;

   pResults->mean = sum / total_values;
   pResults->mean_squared = sum2 / total_values;

   pResults->root_mean_squared = sqrt(pResults->mean_squared);

   if (!pResults->root_mean_squared)
      pResults->peak_snr = 1e+10f;
   else
      pResults->peak_snr = log10(255.0f / pResults->root_mean_squared) * 20.0f;
}

Mam funkci, ktera mi obrazek vrati jako

uint8 *pImage;

Jestli to spravne chapu, tak je to nejake pole s uint8 hodnotami. RGB za sebou, protoze tam je jeste jakasi konverzni funkce (kterou nepouzivam, nepotrebuji), ktera cte data jako (y * width + x) * components.
Potreboval bych to prevest na PPM pixmapu, kterou zobrazuji napriklad jako

QString path1 = "C:\\QT-projekty\\test-proj-j\\jpgcode\\smiley.jpg";
QPixmap pixmap(path1);
ui->label->setPixmap(pixmap);

Pixmapu je tez mozne nacist pomoci 

QByteArray z;
pixmap.loadFromData(z);

pixmapa je prave ve formatu PNM, ktery by melo byt snadne z toho pImage typu RGB dostat. PPM vypada tak, ze k RGB se na zacatek pripoji text 

P6
200 200
255

P asi oznacuje PPM, 6 je pocet komponent, obvykle 6, pro grayscale 5, ale asi by tam slo pouzit i 3.
Pak je sirka vyska obrazku.
255 na konci.

Ted bych potreboval tento spojit retezec + pImage do neceho, treba pImage2 a zkonvertovat to na format pixmap, abych to mohl vykreslit na obrazovku a videt, ze ta funkce generujici pImage skutecne udela obrazek.
Problem je, ze jako zacatecnik se uz snazim druhej den poskladat nejak ten string v QT a prevod formatu se mi uz nedari vubec. To Qt cpp funguje fakt nejak divne. Bud mi to pise errory, coz nejak opravim, a nebo mi pri spusteni aplikace aplikace hapne a nenapise proc. Takze pak nechapu, co se deje.
Pomohl by mi nekdo napsat tu jednoduchou prevodni funkci? Nektere veci se mi asi podarilo vyresit, ale neumim to propojit.

--- to jsou jakesi fragmenty kodu, jak asi by to mohlo vypadat
--- ake proste nechapu, jak s tim to cesko pracuje, jak pridat na zacatek pole typu uint8 nejaky Qstring;
        char result[]="";

        int c;
        int w;
        int h;
        c = decoder.IsColor() ? 6 : 5;
        w = decoder.GetWidth();
        h = decoder.GetHeight();
        //result = "P"+((char*)c)+"\n"+((char*)w)+" "+((char*)h)+"\n255\n";
        strcpy(result,"");
        strcat(result,"P");
        strcat(result,QString::number(c).toLocal8Bit());
        strcat(result,"\n");
        strcat(result,QString::number(w).toLocal8Bit());
        strcat(result," ");
        strcat(result,QString::number(h).toLocal8Bit());
        strcat(result,"\n255\n");
        strcat(result,QString::number(decoder.GetImageSize()).toLocal8Bit());
---
    uchar image2[] = "";
    uchar *pImage2 = image2;
    //image2[] = "";
    //pImage2 = &image2;

    //pImage2 = image1;

    int pos,z,x,y;
    z = 0;
    for (y = 0; y < height; ++y)
    {

       for (x = 0; x < width; ++x)
       {
             pos =  z * comps;
             ++z;
//             pImage +=pos;
             //pImage2+=pos;
             //pImage2[0] = (uchar)pImage[0];
             //pImage2[1] = (uchar)pImage[1];
             //pImage2[2] = (uchar)pImage[2];
       }
    }
--- tohle je original funkce, ktera s tim "pImage" pracuje jako
--- "const uint8 *pSrc", ale konvertuje to do "int a[3];" (to je to "int* pDst")
static void get_pixel(int* pDst, const uint8 *pSrc, int luma_only, int num_comps)
{
   int r, g, b;
   if (num_comps == 1)
   {
      r = g = b = pSrc[0];
   }
   else if (luma_only)
   {
      const int YR = 19595, YG = 38470, YB = 7471;
      r = g = b = (pSrc[0] * YR + pSrc[1] * YG + pSrc[2] * YB + 32768) / 65536;
   }
   else
   {
      r = pSrc[0]; g = pSrc[1]; b = pSrc[2];
   }
   pDst[0] = r; pDst[1] = g; pDst[2] = b;
}