implement anti-aliasing for dump image (and dump movie)

doc/src/dump_image.rst

@@ -103,7 +103,7 @@ Syntax
    dump_modify dump-ID keyword values ...
 
 * these keywords apply only to the *image* and *movie* styles and are documented on this page
-* keyword = *acolor* or *adiam* or *amap* or *gmap* or *backcolor* or *bcolor* or *bdiam* or *bitrate* or *boxcolor* or *color* or *framerate* or *gmap*
+* keyword = *acolor* or *adiam* or *amap* or *gmap* or *backcolor* or *bcolor* or *bdiam* or *bitrate* or *boxcolor* or *color* or *framerate* or *fsaa* or *gmap*
 * see the :doc:`dump modify <dump_modify>` doc page for more general keywords
 
   .. parsed-literal::
@@ -151,6 +151,8 @@ Syntax
          R,G,B = red/green/blue numeric values from 0.0 to 1.0
        *framerate* arg = fps
          fps = frames per second for movie
+       *fsaa* arg = yes/no
+         yes/no = do or do not apply anti-aliasing
        *gmap* args = identical to *amap* args
 
 Examples
@@ -957,6 +959,17 @@ frequently.
 
 ----------
 
+.. versionadded:: TBD
+
+The *fsaa* keyword can be used with the dump image command to improve
+the image quality by enabling full scene anti-aliasing.  Internally the
+image is rendered at twice the width and height and then scaled down by
+computing the average of each 2x2 block of pixels to produce a single
+pixel in the final image at the original size. This produces smoother,
+less ragged edges.
+
+----------
+
 The *gmap* keyword can be used with the dump image command, with its
 *grid* keyword, to setup a color map.  The color map is used to assign
 a specific RGB (red/green/blue) color value to an individual grid cell

src/dump_image.cpp

@@ -1555,6 +1555,35 @@ int DumpImage::modify_param(int narg, char **arg)
     return n;
   }
 
+  // if antialias state changes, we need to increase the buffer space
+  // change the (internal) image dimensions and reset the view parameters
+  if (strcmp(arg[0],"fsaa") == 0) {
+    if (narg < 2) error->all(FLERR,"Illegal dump_modify command");
+    int aa = utils::logical(FLERR, arg[1], false, lmp);
+    if (image->fsaa == NO) {
+      if (aa == YES) {
+        image->width = image->width*2;
+        image->height = image->height*2;
+        // reallocate buffers to make room
+        image->buffers();
+      }
+    } else {
+      if (aa == NO) {
+        image->width = image->width/2;
+        image->height = image->height/2;
+        box_bounds();
+        box_center();
+        view_params();
+      }
+    }
+    image->fsaa = aa;
+    // reset size based parameters
+    box_bounds();
+    box_center();
+    view_params();
+    return 2;
+  }
+
   if (strcmp(arg[0],"bcolor") == 0) {
     if (narg < 3) error->all(FLERR,"Illegal dump_modify command");
     if (atom->nbondtypes == 0)

src/image.cpp

@@ -55,7 +55,9 @@ enum{NO,YES};
 
 /* ---------------------------------------------------------------------- */
 
-Image::Image(LAMMPS *lmp, int nmap_caller) : Pointers(lmp)
+Image::Image(LAMMPS *lmp, int nmap_caller) :
+  Pointers(lmp), depthBuffer(nullptr), surfaceBuffer(nullptr), imageBuffer(nullptr),
+  depthcopy(nullptr),surfacecopy(nullptr),rgbcopy(nullptr)
 {
   MPI_Comm_rank(world,&me);
   MPI_Comm_size(world,&nprocs);
@@ -69,6 +71,7 @@ Image::Image(LAMMPS *lmp, int nmap_caller) : Pointers(lmp)
   persp = 0.0;
   shiny = 1.0;
   ssao = NO;
+  fsaa = NO;
 
   up[0] = 0.0;
   up[1] = 0.0;
@@ -154,6 +157,13 @@ Image::~Image()
 
 void Image::buffers()
 {
+  memory->destroy(depthBuffer);
+  memory->destroy(surfaceBuffer);
+  memory->destroy(imageBuffer);
+  memory->destroy(depthcopy);
+  memory->destroy(surfacecopy);
+  memory->destroy(rgbcopy);
+
   npixels = width * height;
   memory->create(depthBuffer,npixels,"image:depthBuffer");
   memory->create(surfaceBuffer,2*npixels,"image:surfaceBuffer");
@@ -380,6 +390,26 @@ void Image::merge()
   } else {
     writeBuffer = imageBuffer;
   }
+
+  // scale down image for antialiasing. can be done in place with simple averaging
+  if (fsaa) {
+    for (int h=0; h < height; h += 2) {
+      for (int w=0; w < width; w +=2) {
+        int idx1 = 3*height*h + 3*w;
+        int idx2 = 3*height*h + 3*(w+1);
+        int idx3 = 3*height*(h+1) + 3*w;
+        int idx4 = 3*height*(h+1) + 3*(w+1);
+
+        int out = 3*(height/2)*(h/2) + 3*(w/2);
+        for (int i=0; i < 3; ++i) {
+          writeBuffer[out+i] = (unsigned char) (0.25*((int)writeBuffer[idx1+i]
+                                                      +(int)writeBuffer[idx2+i]
+                                                      +(int)writeBuffer[idx3+i]
+                                                      +(int)writeBuffer[idx4+i]));
+        }
+      }
+    }
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -1037,6 +1067,7 @@ void Image::compute_SSAO()
 void Image::write_JPG(FILE *fp)
 {
 #ifdef LAMMPS_JPEG
+  int aafactor = fsaa ? 2 : 1;
   struct jpeg_compress_struct cinfo;
   struct jpeg_error_mgr jerr;
   JSAMPROW row_pointer;
@@ -1044,8 +1075,8 @@ void Image::write_JPG(FILE *fp)
   cinfo.err = jpeg_std_error(&jerr);
   jpeg_create_compress(&cinfo);
   jpeg_stdio_dest(&cinfo,fp);
-  cinfo.image_width = width;
+  cinfo.image_width = width/aafactor;
-  cinfo.image_height = height;
+  cinfo.image_height = height/aafactor;
   cinfo.input_components = 3;
   cinfo.in_color_space = JCS_RGB;
 
@@ -1055,7 +1086,7 @@ void Image::write_JPG(FILE *fp)
 
   while (cinfo.next_scanline < cinfo.image_height) {
     row_pointer = (JSAMPROW)
-      &writeBuffer[(cinfo.image_height - 1 - cinfo.next_scanline) * 3 * width];
+      &writeBuffer[(cinfo.image_height - 1 - cinfo.next_scanline) * 3 * (width/aafactor)];
     jpeg_write_scanlines(&cinfo,&row_pointer,1);
   }
 
@@ -1071,6 +1102,7 @@ void Image::write_JPG(FILE *fp)
 void Image::write_PNG(FILE *fp)
 {
 #ifdef LAMMPS_PNG
+  int aafactor = fsaa ? 2 : 1;
   png_structp png_ptr;
   png_infop info_ptr;
 
@@ -1091,7 +1123,7 @@ void Image::write_PNG(FILE *fp)
 
   png_init_io(png_ptr, fp);
   png_set_compression_level(png_ptr,Z_BEST_COMPRESSION);
-  png_set_IHDR(png_ptr,info_ptr,width,height,8,PNG_COLOR_TYPE_RGB,
+  png_set_IHDR(png_ptr,info_ptr,width/aafactor,height/aafactor,8,PNG_COLOR_TYPE_RGB,
     PNG_INTERLACE_NONE,PNG_COMPRESSION_TYPE_DEFAULT,PNG_FILTER_TYPE_DEFAULT);
 
   png_text text_ptr[2];
@@ -1111,9 +1143,9 @@ void Image::write_PNG(FILE *fp)
   png_set_text(png_ptr,info_ptr,text_ptr,1);
   png_write_info(png_ptr,info_ptr);
 
-  auto row_pointers = new png_bytep[height];
+  auto row_pointers = new png_bytep[height/aafactor];
-  for (int i=0; i < height; ++i)
+  for (int i=0; i < height/aafactor; ++i)
-    row_pointers[i] = (png_bytep) &writeBuffer[(height-i-1)*3*width];
+    row_pointers[i] = (png_bytep) &writeBuffer[((height/aafactor)-i-1)*3*(width/aafactor)];
 
   png_write_image(png_ptr, row_pointers);
   png_write_end(png_ptr, info_ptr);
@@ -1129,11 +1161,12 @@ void Image::write_PNG(FILE *fp)
 
 void Image::write_PPM(FILE *fp)
 {
-  fprintf(fp,"P6\n%d %d\n255\n",width,height);
+  int aafactor = fsaa ? 2 : 1;
+  fprintf(fp,"P6\n%d %d\n255\n",width/aafactor,height/aafactor);
 
   int y;
-  for (y = height-1; y >= 0; y--)
+  for (y = (height/aafactor)-1; y >= 0; y--)
-    fwrite(&writeBuffer[y*width*3],3,width,fp);
+    fwrite(&writeBuffer[y*(width/aafactor)*3],3,width/aafactor,fp);
 }
 
 /* ----------------------------------------------------------------------

src/image.h

@@ -28,6 +28,7 @@ class Image : protected Pointers {
   double zoom;                // zoom factor
   double persp;               // perspective factor
   double shiny;               // shininess of objects
+  int fsaa;                   // antialiasing on or off
   int ssao;                   // SSAO on or off
   int seed;                   // RN seed for SSAO
   double ssaoint;             // strength of shading from 0 to 1