HBBMP - Petewg/harbour-core GitHub Wiki

HBBMP libraray

Copyright 2025 Przemyslaw Czerpak <druzus /at/ priv.onet.pl>
Note: library documentation, provided by author. Reformatted as .md text, to be human-friendly readable (Pete D. 2026-02-12).

HBBMP is small library for Harbour dedicated to create and modify BMP images. It has not any 3rd party libs dependencies. It allows to create new images load existing ones and draw simple graphics primitives. I did not implement more advanced ones to not create math lib dependencies. Anyhow if someone is interesting in it then please implement it. For me this library is enough to work as backend for HBZEBRA library (excellent job of Mindaugas Kavaliauskas). I hope you will find it useful.

Only uncompressed BMP images are supported. When BMP file with compression flag is loaded then UNSUPPORTED error is set. This is the only case when this error can appear.

This library can work images using 1, 4, 8, 16, 24 and 32 color depth (all officially defined). It can work with 2-bit color depth (4 colors) BMP images which are not supported in official documentation. I blocked them inside hb_bmp_new() C function but if someone needs to create such BMP file then it's enough to uncomment one line with "case 2:" in this code. In BMP images with 1, 4 and 8 color depths number of colors is limited to 2, 16 and 256 colors. If limit exceeds or unsupported colors are defined then -1 is returned and error is set. In BMP images with 24 color depth alpha channel does not exists and this library silently ignores it when user pass it in color index. BMP images with 16-bit color depth does not have RGB color table so only arbitrary color indexes can be used and their real colors necessary for visualization have to be defined outside BMP file. BMP images color depth 24 and 32 do not use color table and color indexes are pure big endian RGB values with optional alpha channel which is ignored in case of 24 bit depth (0xAARRGGBB) so it's not necessary to allocate colors and programmer may use it directly, i.e. red := 0xFF0000 The color and alpha must be in range from 0 to 255. When new BMP is created user can change the order in which rows are stored in memory and files from bottom-up to top-down setting the image height to negative value.

On PRG level the BMP image structure is represented as pointer item with attached destructor so when last variable (Harbour item) pointing to given BMP structure is cleared or overwritten (f.e. by pBMP := NIL) then destructor is called and BMP image structure removed from memory. Anyhow it's possible to force release operation by explicit call to hb_bmp_free().

The following PRG functions exist in HBBMP lib:

hb_bmp_color(<pBMP>, <nRed>, <nGreen>, <nBlue>, <nAlpha>) => nColor | -1

   → Allocate new color or take index to existing one, or error -1 is returned.

hb_bmp_color2rgb(<pBMP>, <nColor>, @<nRed>, @<nGreen>, @<nBlue>, @<nAlpha>) => lOK

   → Convert color index to its RGB value, return .T. on success or .F. in case of error.

hb_bmp_copy( <pBMPsrc> ) => pBMPcopy

   → Make independent copy of memory BMP structures.

hb_bmp_decode(<cBMPdata>, [@<nError>]) => pBMP | NIL

   → Create new BMP image structure from passed BMP file body, return pointer item BMP structure or NIL on error.

hb_bmp_depth(<pBMP>) => nDepth

   → Get BMP color depth.

hb_bmp_encode(<pBMP>) => cBMPdata

   → Create BMP file body from BMP image structure.

hb_bmp_free( <pBMP> ) --> NIL

   → Free BMP structure from memory.

hb_bmp_getpixel(<pBMP>, <nX>, <nY>) => nColor

   → Get color index of pixel at given coordinates, on error -1 is returned.

hb_bmp_height(<pBMP>) => nHeight

   → Get BMP height.

hb_bmp_line(<pBMP>, <nX1>, <nY1>, <nX2>, <nY2>, <nColor>) => NIL

   → Draw line from the given starting and ending points and color index.

hb_bmp_load(<cFileName>, [@<nError>]) => pBMP | NIL

   → Load BMP image from file, return pointer item BMP image structure or NIL on error

hb_bmp_new( <nWidth>, <nHeight>, [<nDepth>=1], [<nDPI>=72], [@<nError>] ) → pBMP | NIL (error indicator)

   → Create new BMP in memory, return pointer item or NIL on error.

hb_bmp_putpixel(<pBMP>, <nX>, <nY>, <nColor>) => lOK

   → Set pixel using given coordinates and color index.

hb_bmp_rect(<pBMP>, <nX>, <nY>, <nWidth>, <nHeight>, <nColor>, [<lFill>=.t.]) => NIL

   → Draw rectangle (filled by default) using given coordinates, size and index color.

hb_bmp_save(<pBMP>, <cFileName>) => lOK

   → Save BMP image into file.

hb_bmp_width(<pBMP>) => nWidth

   → Get BMP width.

the sunset's small sailing boat Harbour Functions Dictionary   Many of the entries presented in this wiki, have been obtained from various sources (see References); however, a good number of them have been written «from scratch» (or rewritten/corrected), particularly those referring to newer Harbour functions. Anyway, it's a 'work in progress', so there might be omissions, oversights and / or errors. That said, any suggestion/correction/comment are more than welcome --many thanks, to those few who already have made contributions!

 * Copyright © 2016–present Pete D.
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