.CDR File Format – Preview picture

CorelDRAW drawing

A RIFF CorelDRAW file carries a small picture of the drawing in a DISP chunk, straight after vrsn, so a program can show it without reading the drawing. The ZIP packages of X4 and later keep a PNG thumbnail instead.

Layout

Offsets count from the start of the chunk’s data, after its ID and length.

  1. 0Unknown libcdr steps over these four bytes4 bytes
  2. 4Bitmap header a BITMAPINFOHEADER: size 40, width, height, planes, bits per pixel, compression, image size, resolution, colours40 bytes
  3. 44Colour table four bytes a colour (blue, green, red, 0), for 8 bits a pixel or fewervaries
  4. …Pixels rows from the bottom up, each padded to four bytesimage size
A DISP chunk is a device-independent bitmap, the body of a .bmp file without its 14-byte file header, after four bytes.

To make a .bmp file from it, libcdr writes BM, the chunk length plus 8, four zero bytes and the offset of the pixels (the chunk length plus 10, less the image size from the header), then the chunk’s data from offset 4.