Dr Dave

I previously discussed a command-line tool for generating image tiles. I've updated the tool to include an additional parameter for image format. Usage is as follows, and the tool is available for download:

C:\tilegen /?
Generates a directory of tiles from a source image equirectangular projection

TILEGEN [drive:][path]filename level [/S=size] [/D=directory] [/F=filename] [/I=image]

   [drive:][path]filename   Soure image
   level                    Level of detail (0-based)
   /S=size                  Size of tile, default 256px
   /D=directory             Directory format, default level{0}
   /F=filename              Filename format, default {col}_{row}
   /I=image                 Image format (JPEG, PNG, TIFF), default JPEG (Compression=90)

Note that the source image is not scaled so must be correct level and size,
i.e. width (px) = 2 * 2^level * size, height (px) = 2^level * size

C:\>

I needed to create image tiles to provide textures for level of detail rendering of planetary bodies. After looking around for a bit, I decided to write a simple tool for the job. For equirectangular¹ projections, all I needed was to load big images and chop them up into a number of tiles according to a naming convention.

I decided not to support image resizing, as there are plenty of tools available which can do the job with an appropriate filter for the type of image.

The System.Drawing namespace can load big images using Bitmap.FromFile(), providing the image fits into memory, which in practical terms means Windows 64bit. The Graphics.DrawImageUnscaled() method can then be used to draw a tile, providing I maintain the dpi of the source image.

The command-line version is available for download. Usage is as follows:

C:\Tiles>tilegen /?
Generates a directory of tiles from a source image equirectangular projection

TILEGEN [drive:][path]filename level [/S=size] [/D=directory] [/F=filename]

   [drive:][path]filename   Soure image
   level                    Level of detail (0-based)
   /S=size                  Size of tile, default 256px
   /D=directory             Directory format, default level{0}
   /F=filename              Filename format, default {col}_{row}

Note that the source image is not scaled so must be correct level and size,
i.e. width (px) = 2 * 2^level * size, height (px) = 2^level * size

C:\Tiles>

To generate 8x256px tiles at level 1 from an appropriately-named 1024x512px image, I use:

C:\Tiles>tilegen 1024x512.jpg 1
Loading source image...done, 0.02s
Creating folder...done
Generating tile 8/8...done, 0.05s

C:\Tiles>

The optional parameters allow generation of different tile sizes, and output of custom directory and file path names.

¹ Equirectangular is also known as Simple Cylindrical and Plate Carrée.