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Bitmaps provide the pixel patterns used by pictures, icons and masks, sprites and brush styles for filling areas of the display. To optimise bitmap handling performance, EPOC uses files containing multiple bitmaps in its own EPOC bitmap format. These files are of two types:
The bmconv tool is used to convert bitmaps designed on a PC to EPOC bitmap format. The tool is also used to perform the reverse conversion process, so bitmaps can be created on either platform.
Note that the tools are used for converting bitmaps files prior to bundling in EPOC installation files — see Preparing applications for installation. Microsoft Windows bitmap files are automatically converted to EPOC Sketch files, and visa versa, when files are moved between EPOC and a PC using EPOC Connect.
bmconv in EPOC Release 5The bmconv bitmap conversion tool has increased functionality, primarily to support enhancements, such as colour, to EPOC.
The new arguments available to bmconv in this release are: /n, /q, /bpp, and /v. Pre EPOC release 5, bmconv was limited to creating 1, 2 or 4 bits per pixel bitmaps. It can now create bitmaps for all the new display EPOC modes.
Section Contents
Making a file of bitmaps for use by EPOC consists of two stages:
.bmp format.The following example shows the creation of an EPOC multi-bitmap file from three Windows bitmaps, created using Microsoft Paintbrush. They can be found in \epoc32ex\adk\.
The most important feature to consider when designing a bitmap is the capacity of the target system. While bmconv can convert 24-bit colour bitmaps to .mbm format, there is little point in doing so if the EPOC platform can only display 4-bit images. In addition, increased colour depth comes at the cost of increased file size, and should be used sparingly.
The smallest memory/least colour diagrams are those produced in monochrome, e.g. black and white. The diagram \epoc32ex\adk\hangman.bmp was produced in Microsoft Paintbrush, and then saved as monochrome bitmap using:
File|Save As...|Monochrome bitmap (*.BMP)
The second examples are the 16 colour bitmaps smiley.bmp and abstract.bmp. These were drawn in various colours and shades of grey, and then saved using:
File|Save As...|16 Color bitmap (*.BMP)
The .bmp files must be converted into EPOC format bitmaps and combined into a multi-bitmap file. A possible command line to use is:
bmconv /hbmexmpl.h bmexmpl.mbm /4smiley.bmp /1hangman.bmp /c16abstract.bmp
The screen output should be:
BMCONV version 48.
Compiling...
Multiple bitmap store type: File store
Epoc file: bmexmpl.mbm
Bitmap file 1 : Smiley.bmp
Bitmap file 2 : Hangman.bmp
Bitmap file 3 : Abstract.bmp
Success.
The header file generated is as follows:
// bmexmpl.h
// Generated by BitmapCompiler
// Copyright (c) 1998 Symbian Ltd
//
enum TMbmBmexmpl
{
EMbmBmexmplSmiley,
EMbmBmexmplHangman,
EMbmBmexmplAbstract
};
The contents of a file can be viewed using the summary switch /v , as shown below:
bmconv /v bmexmpl.mbm
This results in a screen output:
BMCONV version 48.
Bitmap 1 information:
Pixel size 48 x 48
Twips size 0 x 0
4 Bpp Monochrome
Bytewise RLE compression 45%
Bitmap 2 information:
Pixel size 33 x 33
Twips size 49 x 49
1 Bpp Monochrome
Bytewise RLE compression 59%
Bitmap 3 information:
Pixel size 216 x 158
Twips size 323 x 236
16 Bpp Colour
16 bit RLE compression 5%
bmexmpl.mbm contains 3 bitmaps
.bmp format. This is independent of the resolution of the original bitmap.Windows bitmap files can be extracted from a multi-bitmap file using the /u switch, as shown below:
bmconv /u bmexmpl.mbm smiley-out.bmp hangman-out.bmp abstract-out.bmp
This results in a screen output:
BMCONV version 48.
Decompiling...
Epoc file: bmexmpl.mbm
Bitmap file 1 : smiley-out.bmp
Bitmap file 2 : hangman-out.bmp
Bitmap file 3 : abstract-out.bmp
Success.
.mbm. Any name can be used, however a .bmp extension should be declared so that Windows will associate the bitmap with a viewer.
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