xref: /petsc/src/sys/classes/draw/impls/x/ximage.c (revision cf9512e468810271e605c7107b28f68f448f0948)

/*
    Code for getting raster images out of a X image or pixmap
*/

#include <../src/sys/classes/draw/impls/x/ximpl.h>

PETSC_INTERN PetscErrorCode PetscDrawGetImage_X(PetscDraw, unsigned char[PETSC_DRAW_MAXCOLOR][3], unsigned int *, unsigned int *, unsigned char *[]);

static inline PetscErrorCode PetscArgSortPixVal(const PetscDrawXiPixVal v[PETSC_DRAW_MAXCOLOR], int idx[], int right)
{
  PetscDrawXiPixVal vl;
  int               i, last, tmp;
#define SWAP(a, b) \
  do { \
    tmp = a; \
    a   = b; \
    b   = tmp; \
  } while (0)
  PetscFunctionBegin;
  if (right <= 1) {
    if (right == 1) {
      if (v[idx[0]] > v[idx[1]]) SWAP(idx[0], idx[1]);
    }
    PetscFunctionReturn(PETSC_SUCCESS);
  }
  SWAP(idx[0], idx[right / 2]);
  vl   = v[idx[0]];
  last = 0;
  for (i = 1; i <= right; i++)
    if (v[idx[i]] < vl) {
      last++;
      SWAP(idx[last], idx[i]);
    }
  SWAP(idx[0], idx[last]);
  PetscCall(PetscArgSortPixVal(v, idx, last - 1));
  PetscCall(PetscArgSortPixVal(v, idx + last + 1, right - (last + 1)));
#undef SWAP
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
   Map a pixel value to PETSc color value (index in the colormap)
*/
static inline int PetscDrawXiPixelToColor(PetscDraw_X *Xwin, const int arg[PETSC_DRAW_MAXCOLOR], PetscDrawXiPixVal pix)
{
  const PetscDrawXiPixVal *cmap = Xwin->cmapping;
  int                      lo, mid, hi = PETSC_DRAW_MAXCOLOR;
  /* linear search the first few entries */
  for (lo = 0; lo < 8; lo++)
    if (pix == cmap[lo]) return lo;
  /* binary search the remaining entries */
  while (hi - lo > 1) {
    mid = lo + (hi - lo) / 2;
    if (pix < cmap[arg[mid]]) hi = mid;
    else lo = mid;
  }
  return arg[lo];
}

PetscErrorCode PetscDrawGetImage_X(PetscDraw draw, unsigned char palette[PETSC_DRAW_MAXCOLOR][3], unsigned int *out_w, unsigned int *out_h, unsigned char *out_pixels[])
{
  PetscDraw_X *Xwin = (PetscDraw_X *)draw->data;
  PetscMPIInt  rank;

  PetscFunctionBegin;
  if (out_w) *out_w = 0;
  if (out_h) *out_h = 0;
  if (out_pixels) *out_pixels = NULL;
  PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)draw), &rank));

  /* make sure the X server processed requests from all processes */
  PetscDrawCollectiveBegin(draw);
  XSync(Xwin->disp, True);
  PetscDrawCollectiveEnd(draw);
  PetscCallMPI(MPI_Barrier(PetscObjectComm((PetscObject)draw)));

  /* only the first process return image data */
  PetscDrawCollectiveBegin(draw);
  if (rank == 0) {
    Window         root;
    XImage        *ximage;
    int            pmap[PETSC_DRAW_MAXCOLOR];
    unsigned char *pixels = NULL;
    unsigned int   w, h, dummy;
    int            x, y, p;
    /* copy colormap palette to the caller */
    PetscCall(PetscMemcpy(palette, Xwin->cpalette, sizeof(Xwin->cpalette)));
    /* get image out of the drawable */
    XGetGeometry(Xwin->disp, PetscDrawXiDrawable(Xwin), &root, &x, &y, &w, &h, &dummy, &dummy);
    ximage = XGetImage(Xwin->disp, PetscDrawXiDrawable(Xwin), 0, 0, w, h, AllPlanes, ZPixmap);
    PetscCheck(ximage, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Cannot XGetImage()");
    /* build indirect sort permutation (a.k.a argsort) of the color -> pixel mapping */
    for (p = 0; p < PETSC_DRAW_MAXCOLOR; p++) pmap[p] = p; /* identity permutation */
    PetscCall(PetscArgSortPixVal(Xwin->cmapping, pmap, 255));
    /* extract pixel values out of the image and map them to color indices */
    PetscCall(PetscMalloc1(w * h, &pixels));
    for (p = 0, y = 0; y < (int)h; y++)
      for (x = 0; x < (int)w; x++) {
        PetscDrawXiPixVal pix = XGetPixel(ximage, x, y);
        pixels[p++]           = (unsigned char)PetscDrawXiPixelToColor(Xwin, pmap, pix);
      }
    XDestroyImage(ximage);
    *out_w      = w;
    *out_h      = h;
    *out_pixels = pixels;
  }
  PetscDrawCollectiveEnd(draw);
  PetscFunctionReturn(PETSC_SUCCESS);
}