local bmp = require'bmp'

BMP file loading and saving module. Supports all file header versions, color depths and pixel formats and encodings except very rare ones (embedded JPEGs, embedded PNGs, OS/2 headers, RLE deltas). Supports progressive loading, yielding from the reader and writer functions and saving in bgra8 format.

API

bmp.open(read) -> b|nil,err	open a BMP file and read it’s header
b.w	width
b.h	height
b.bpp	bits per pixel
b:load(bmp[, x, y]) -> bmp | nil,err	load/paint the pixels into a given bitmap
b:load(format, ...) -> bmp | nil,err	load the pixels into a new bitmap
b:rows(bmp | format,...) -> iter() -> i, bmp	iterate the rows over a 1-row bitmap
bmp.save(bmp, write) -> ok | nil,err	save a bitmap using a write function

bmp.open(read) -> b|nil,err

Open a BMP file. The read function has the form read(buf, len) -> readlen, it can yield and it can signal I/O errors by returning nil, err. It will only be asked to read a positive number of bytes and it can return less bytes than asked, including zero which signals EOF.

b:load(bmp[, x, y]) -> bmp | nil,err

Load and paint the bmp’s pixels into a given bitmap, optionally at a specified position within the bitmap. All necessary format conversions and clipping are done via the bitmap module.

b:load(format, ...) -> bmp | nil,err

Load the bmp’s pixels into a new bitmap of a specified format. Extra arguments are passed to bitmap.new().

b:rows(bmp | format,...) -> iter() -> i, bmp

Iterate the bmp’s rows over a new or provided 1-row bitmap. The row index is decreasing if the bitmap is bottom-up. Unlike b:load(), this method and the returned iterator are not protected (they raise errors).

bmp.save(bmp, write) -> true | nil, err

Save bmp file using a write(buf, size) function to write the bytes. The write function should accept any size >= 0 and it should raise an error if it can’t write all the bytes.

Low-level API

b.bottom_up	are the rows stored bottom up?
b.compression	encoding type
b.transparent	does it use the alpha channel?
b.palettized	does it use a palette?
b.bitmasks	RGBA bitmasks (BITFIELDS encoding)
b.rle	is it RLE-encoded?
b:load_pal() -> ok|nil,err	load the palette
b:pal_entry(index) -> r, g, b, a	palette lookup (loads the palette)
b.pal_count -> n	palette color count

Last updated: 17 months ago | Edit on GitHub