Add instructions and 'double fisheye' support

README.md

@@ -0,0 +1,49 @@
+# Dual Fisheye to Equirectangular Projection Mapping
+
+Many '360' camera's, such as the [dokicam](http://dokicam.com/), consist of 2
+fish-eye camera's. 
+
+## Why DIY?
+
+Those camera's typically come with desktop software or apps
+to manipulate the images and for example share to facebook.
+
+It's fun to explore doing this without relying on the official software. 
+
+## Storage
+
+The dokicam stores its photos and videos on its memory card in JPG and MP4
+format, easily accessible via USB storage without even removing the card.
+
+## Projection conversion
+
+Those images and video's show the 'double fish-eye' nature of the device.
+Services like Facebook, however require, require 306 imagery to be mapped
+using the Equirectangular Projection. This can be achieved with `ffmpeg`
+using 2 'mapping files' for your image type.
+
+## Mapping generation
+
+I did not find a suitable mapping for my camera online. However I did find
+`projection.c` by Floris Sluiter which could generate such mapping files
+for single-fisheye sources, and modified it to support double-fisheye.
+
+Compile the generator code:
+
+    gcc -o projection projection.c -lm
+
+Create mapping files for video and photo's:
+
+    ./projection -x xmap_dokicam_video.pgm -y ymap_dokicam_video.pgm -h 1440 -w 2880 -r 1440 -c 2880 -b 35 -m double
+    ./projection -x xmap_dokicam.pgm -y ymap_dokicam.pgm -h 2048 -w 4096 -r 2048 -c 4096 -b 75 -m double
+
+## Usage
+
+Once you have created (or downloaded) the mapping files, use them with ffmpeg:
+
+    ffmpeg -i photo.jpg -i xmap_dokicam.pgm -i ymap_dokicam.pgm -filter_complex remap out.jpg
+    ffmpeg -i movie.mp4 -i xmap_dokicam_video.pgm -i ymap_dokicam_video.pgm -filter_complex remap out.mp4
+
+For images, add exif metadata to help e.g. Facebook understand this is 360:
+
+    exiftool -ProjectionType="equirectangular" out.jpg

projection.c

@@ -27,6 +27,7 @@ typedef struct double3{
 
 enum CameraMode {
     FRONT,
+    DOUBLE,
     FRONT235,
     BACK,
     UP,
@@ -161,6 +162,9 @@ configuration parse_options(int argc, char **argv){
           else if (strcmp(optarg, "thetas") == 0)
           {
             po.mode = THETAS;
+          } else if (strcmp(optarg, "double") == 0)
+          {
+            po.mode = DOUBLE;
           }
           /* more else if clauses */
           else /* default: */
@@ -188,6 +192,7 @@ configuration parse_options(int argc, char **argv){
   if(verbose_flag){
     switch(po.mode){
       case FRONT:   printf("Camera: Front proj\n"); break;
+      case DOUBLE: printf("Camera: Double fisheye proj\n"); break;
       case FRONT235:   printf("Camera: Front 235 proj\n"); break;
       case DOWN:   printf("Camera: Down proj\n"); break;
       case SAMSUNG_GEAR_360: printf("Camera: samsung_gear_360\n"); break;
@@ -318,6 +323,24 @@ void gen_front_maps(configuration cfg,int** image_x,int** image_y ){
   }
 }
 
+void gen_double_maps(configuration cfg, int** image_x, int** image_y) {
+  int x,y;
+  // width of a 'single' fisheye in the input, uncropped
+  int single_width = cfg.width / 2;
+  int single_cols = cfg.cols / 2;
+
+  for (y = 0; y<cfg.rows;y++){
+    for (x = 0; x < cfg.cols; x++){
+      int xcrop = x < single_cols ? single_cols + cfg.crop : cfg.crop;
+      int single_x = x % single_cols;
+      double2 o = evaluatePixel_Front((double2){((double)single_x/((double)single_cols)) * ((single_width)-(2*cfg.crop)),
+                                                ((double)y/(double)cfg.rows)   * ((cfg.height)  -(2*cfg.crop))},
+                                      (double2){(single_width)-(2*cfg.crop), cfg.height-(2*cfg.crop)});
+      image_x[y][x] = (int)round(o.x)+xcrop;
+      image_y[y][x] = (int)round(o.y)+cfg.crop;
+    }
+  }
+}
 
 int
 main (int argc, char **argv)
@@ -339,6 +362,7 @@ main (int argc, char **argv)
 
     switch(cfg.mode){
       case FRONT:    gen_front_maps(cfg,image_x,image_y); break;
+      case DOUBLE: gen_double_maps(cfg, image_x, image_y); break;
 /*      case FRONT235:    gen_front235_maps(cfg,image_x,image_y); break;
       case DOWN:    gen_down_maps(cfg,image_x,image_y); break;
       case SAMSUNG_GEAR_360: gen_samsung_gear_360_maps(cfg,image_x,image_y); break;