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334 lines
12 KiB
Lua
334 lines
12 KiB
Lua
; Routines to load and save "BMX" files (commander X16 bitmap format) Version 1.
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; Only uncompressed images are supported for now.
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; BMX Specification: https://cx16forum.com/forum/viewtopic.php?t=6945
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; TODO: ability to save "stamps" , bitmaps that are only a region of the screen.
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; TODO: ability to just load the palette from a BMX file
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%import diskio
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bmx {
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ubyte[32] header
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str FILEID = petscii:"bmx"
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ubyte bitsperpixel ; consider using set_bpp() when setting this
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ubyte vera_colordepth ; consider using set_vera_colordepth() when setting this
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uword width
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uword height
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ubyte border
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uword palette_entries ; 1-256
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ubyte palette_start
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ubyte compression
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uword palette_buffer_ptr = 0 ; should you want to load or save the palette into main memory instead of directly into vram
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uword error_message ; pointer to error message, or 0 if all ok
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ubyte old_drivenumber
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sub open(ubyte drivenumber, str filename) -> bool {
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; Open a BMX bitmap file and reads the header information.
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; Returns true if all is ok, false otherwise + error_message will be set.
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error_message = 0
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old_drivenumber = diskio.drivenumber
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diskio.drivenumber = drivenumber
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if diskio.f_open(filename) {
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diskio.reset_read_channel()
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if read_header() {
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if parse_header() {
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if palette_entries>0 {
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if width<=640 {
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return true
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} else
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error_message = "image too large"
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} else
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error_message = "invalid bmx file"
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} else
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error_message = "invalid bmx file"
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} else
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error_message = "invalid bmx file"
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} else
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error_message = diskio.status()
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close()
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return false
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}
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sub close() {
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; if you want to close the file before actually loading palette or bitmap data.
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diskio.f_close()
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diskio.drivenumber = old_drivenumber
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}
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sub continue_load(ubyte vbank, uword vaddr) -> bool {
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; Continues loading the palette and bitmap data from the opened BMX file.
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; Parameters: the vram bank and address where the bitmap data should go.
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; You can set palette_buffer_ptr if you want the palette buffered rather than directly into vram.
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; Note: does not change vera screen mode or colordepth! You have to do that yourself!
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; Returns true if all is ok, false otherwise + error_message will be set.
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error_message = 0
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diskio.reset_read_channel()
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if width==320 or width==640 {
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if compression==0 {
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if read_palette() {
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if not read_bitmap(vbank, vaddr)
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error_message = "bitmap error"
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} else
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error_message = "palette error"
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} else
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error_message = "compression not supported"
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} else
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error_message = "width not 320 or 640" ; note: use continue_load_stamp() to read other sizes
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close()
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return error_message==0
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}
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sub continue_load_stamp(ubyte vbank, uword vaddr, uword screenwidth) -> bool {
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; Continues loading the palette and bitmap "stamp" data from the opened BMX file.
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; "Stamp" means: load an image that is smaller than the screen (so we need to pad around it)
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; Parameters:the vram bank and address where the bitmap data should go,
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; and the screen width that the stamp image is loaded into.
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; You can set palette_buffer_ptr if you want the palette buffered rather than directly into vram.
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; Note: does not change vera screen mode or colordepth! You have to do that yourself!
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; Returns true if all is ok, false otherwise + error_message will be set.
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error_message = 0
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diskio.reset_read_channel()
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if compression==0 {
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if read_palette() {
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if not read_bitmap_padded(vbank, vaddr, screenwidth)
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error_message = "bitmap error"
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} else
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error_message = "palette error"
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} else
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error_message = "compression not supported"
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close()
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return error_message==0
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}
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sub save(ubyte drivenumber, str filename, ubyte vbank, uword vaddr) -> bool {
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; Save bitmap and palette data from vram into a BMX file.
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; First you must have set all bmx.* variables to the correct values! (like width, height..)
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; Parameters:
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; drive number and filename to save to,
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; vram bank and address of the bitmap data to save.
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; Returns: success status. If false, error_message points to the error message string.
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; TODO: how to save bitmaps that are not the full visible screen width (non-contiguous scanlines)?
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if compression {
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error_message = "compression not supported"
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return false
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}
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error_message = 0
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if width!=320 and width!=640 {
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error_message = "width not 320 or 640"
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goto save_end
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}
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old_drivenumber = diskio.drivenumber
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diskio.drivenumber = drivenumber
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if diskio.f_open_w(filename) {
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cx16.r0 = diskio.status()
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if cx16.r0[0]!='0' {
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error_message = cx16.r0
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goto save_end
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}
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diskio.reset_write_channel()
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if write_header() {
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if write_palette() {
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if not write_bitmap(vbank, vaddr)
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error_message = "bitmap error"
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} else
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error_message = "palette error"
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} else
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error_message = "header error"
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} else
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error_message = diskio.status()
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save_end:
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diskio.f_close_w()
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diskio.drivenumber = old_drivenumber
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return error_message==0
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}
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sub set_bpp(ubyte bpp) {
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ubyte[8] depths = [0,1,1,2,2,2,2,3]
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vera_colordepth = depths[bpp-1]
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}
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sub set_vera_colordepth(ubyte depth) {
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vera_colordepth = depth
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bitsperpixel = 1 << depth
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}
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; ------------------- helper routines, usually not needed to call yourself -------------------------
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sub read_header() -> bool {
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; load a BMX header from the currently active input file
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for cx16.r0L in 0 to sizeof(header)-1 {
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header[cx16.r0L] = cbm.CHRIN()
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}
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return not cbm.READST()
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}
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sub read_palette() -> bool {
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; load palette data from the currently active input file
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; if palette_buffer_ptr is not 0, the palette data is read into that memory buffer,
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; otherwise it is read directly into the palette in vram.
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cx16.vaddr(1, $fa00+palette_start*2, 0, 1)
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cx16.r3 = palette_buffer_ptr
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cx16.r2L = lsb(palette_entries)
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do {
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cx16.r4L = cbm.CHRIN()
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cx16.r4H = cbm.CHRIN()
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if cx16.r3 {
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pokew(cx16.r3, cx16.r4) ; into memory
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cx16.r3+=2
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} else {
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cx16.VERA_DATA0 = cx16.r4L ; into vram
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cx16.VERA_DATA0 = cx16.r4H
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}
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cx16.r2L--
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} until cx16.r2L==0
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return cbm.READST()==0 or cbm.READST()&$40 ; no error or eof?
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}
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sub read_bitmap_padded(ubyte vbank, uword vaddr, uword screenwidth) -> bool {
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; load bitmap "stamp" into vram from the currently active input file
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cx16.r3 = bytes_per_scanline(width) ; num bytes per image scanline
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cx16.r2 = bytes_per_scanline(screenwidth) ; num bytes per screen scanline
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repeat height {
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cx16.vaddr(vbank, vaddr, 0, 1)
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read_scanline(cx16.r3)
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vaddr += cx16.r2
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if_cs
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vbank++
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}
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return cbm.READST()==0 or cbm.READST()&$40 ; no error or eof?
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}
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sub read_bitmap(ubyte vbank, uword vaddr) -> bool {
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; load contiguous bitmap into vram from the currently active input file
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cx16.r3 = bytes_per_scanline(width)
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cx16.vaddr(vbank, vaddr, 0, 1)
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repeat height
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read_scanline(cx16.r3)
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return cbm.READST()==0 or cbm.READST()&$40 ; no error or eof?
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}
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sub read_scanline(uword size) {
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while size {
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cx16.r0 = cx16.MACPTR(min(255, size) as ubyte, &cx16.VERA_DATA0, true)
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if_cs {
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; no MACPTR support
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repeat size
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cx16.VERA_DATA0 = cbm.CHRIN()
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return
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}
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size -= cx16.r0
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}
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}
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sub write_header() -> bool {
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; save out the BMX header to the currently active output file
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build_header()
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for cx16.r0L in 0 to sizeof(header)-1 {
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cbm.CHROUT(header[cx16.r0L])
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}
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return not cbm.READST()
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}
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sub write_palette() -> bool {
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; write palette data to the currently active input file
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; if palette_buffer_ptr is not 0, the palette data is read from that memory buffer,
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; otherwise it is read directly from the palette in vram.
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cx16.r3 = palette_buffer_ptr
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cx16.r2L = lsb(palette_entries)
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cx16.vaddr(1, $fa00+palette_start*2, 0, 1)
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do {
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if cx16.r3 {
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cbm.CHROUT(@(cx16.r3)) ; from memory
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cx16.r3++
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cbm.CHROUT(@(cx16.r3))
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cx16.r3++
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} else {
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cbm.CHROUT(cx16.VERA_DATA0) ; from vram
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cbm.CHROUT(cx16.VERA_DATA0)
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}
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cx16.r2L--
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} until cx16.r2L==0
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return not cbm.READST()
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}
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sub write_bitmap(ubyte vbank, uword vaddr) -> bool {
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; save contiguous bitmap from vram to the currently active output file
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cx16.vaddr(vbank, vaddr, 0, 1)
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cx16.r3 = bytes_per_scanline(width)
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repeat height
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write_scanline(cx16.r3)
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return not cbm.READST()
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sub write_scanline(uword size) {
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while size {
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cx16.r0L = lsb(size)
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if msb(size)
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cx16.r0L = 0 ; 256 bytes
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cx16.r0 = cx16.MCIOUT(cx16.r0L, &cx16.VERA_DATA0, true)
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if_cs {
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; no MCIOUT support
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repeat size
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cbm.CHROUT(cx16.VERA_DATA0)
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return
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}
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size -= cx16.r0
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}
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}
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}
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sub bytes_per_scanline(uword w) -> uword {
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ubyte[4] shifts = [3,2,1,0]
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return w >> shifts[vera_colordepth]
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}
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sub parse_header() -> bool {
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if header[0]==FILEID[0] and header[1]==FILEID[1] and header[2]==FILEID[2] {
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if header[3]==1 { ; only version 1 supported for now
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bitsperpixel = header[4]
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vera_colordepth = header[5]
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width = peekw(&header+6)
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height = peekw(&header+8)
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palette_entries = header[10]
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if palette_entries==0
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palette_entries=256
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palette_start = header[11]
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; the data offset is not needed: data_offset = peekw(&header+12)
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compression = header[14]
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border = header[15]
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return true
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}
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}
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return false
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}
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sub build_header() {
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; build the internal BMX header structure
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; normally you don't have to call this yourself
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sys.memset(header, sizeof(header), 0)
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uword data_offset = palette_entries*$0002
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data_offset += sizeof(header)
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header[0] = FILEID[0]
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header[1] = FILEID[1]
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header[2] = FILEID[2]
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header[3] = 1 ; version 1
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header[4] = bitsperpixel
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header[5] = vera_colordepth
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header[6] = lsb(width)
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header[7] = msb(width)
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header[8] = lsb(height)
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header[9] = msb(height)
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header[10] = lsb(palette_entries)
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header[11] = palette_start
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header[12] = lsb(data_offset)
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header[13] = msb(data_offset)
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header[14] = compression
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header[15] = border
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}
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}
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