Editing Image Formats (section)

=== Headers ===
Each Doom picture starts with a header, indexing the offsets of each column. When a picture is rendered, the engine starts drawing each column at the offset given in <code>columnofs</code> and draws all posts it finds until the next column starting with <code>0xFF</code> (column terminator byte).
{| class="wikitable"
|+
Patch header data structure
!Field
!Type
!Byte size
!Byte offset
!Description
|-
|width
|uint16_t
|2
|0
|Graphic width (Little Endian)
|-
|height
|uint16_t
|2
|2
|Graphic height (Little Endian)
|-
|leftoffset
|int16_t
|2
|4
|Pixel offset from the left side (Little Endian)
|-
|topoffset
|int16_t
|2
|6
|Pixel offset from the top (Little Endian)
|-
|columnofs
|uint32_t[]
|4 * width
|8
|Array of column offsets relative to the beginning of this header (Little Endian)
|}