madNVBitmap Unit

Usually when dealing with bitmaps you're using "Graphics.pas". madExcept doesn't use that, because that would mean linking all the VCL stuff in. Furthermore "Graphics" doesn't support all the features which madExcept needs. So I've decided to create a whole new unit which implements exactly that part of functionality which I need for madExcept without using any VCL units. The resulting unit is named "madNVBitmap" ("NV" stands for "non VCL"). For a list of what's contained in this unit please look at the madNVBitmap Reference.

All the functionality is available through the "INVBitmap" interface. There are two ways to get an instance of this interface: You can either load a bitmap from harddisk, or you can ask madNVBitmap to capture the current screen content. Both "LoadBitmap" and "ScreenShot" return "nil", if they fail.

  INVBitmap = interface ['{3EE757B5-CC56-4610-A917-E8731737D5BE}'];

// load a *.bmp file from harddisk
function LoadBitmap (bmpFile: string) : INVBitmap;

// capture the current screen content
function ScreenShot (thisAppOnly: boolean = false) : INVBitmap;

Once you have a valid INVBitmap instance, you can ask the width and height of the encapsulated bitmap. The color depth is always "true color".

property INVBitmap.Width  : integer;
property INVBitmap.Height : integer;

What is the main purpose of a bitmap? Of course to show/draw it somewhere:

function INVBitmap.Draw (dc: dword; x, y: integer) : boolean;

One nice functionality offered by madNVBitmap is smooth scaling of the bitmap. The scaling uses the high quality "Mitchell" filter. Resizing is always done in a way that doesn't change the aspect ratio of the original bitmap. E.g. if you call "Zoom(32, 32)" on a 800x600 bitmap, then the resulting bitmap will have a size of 32x24. Calling "Zoom" does not change the current bitmap, instead is creates and returns a new INVBitmap instance for the resized bitmap.

function INVBitmap.Zoom (width, height: integer) : INVBitmap;

Finally we can save our bitmap in either "bmp" or "png" format. When saving in "png" format you can choose between some compression modes. Generally you can either save in 16 gray shades or in 256 colors, or you can let madNVBitmap decide for itself which mode to use, depending on how big the resulting "png" file would get in either mode.

  TPngFormat = (pf256Colors, pf16Grays, pf50kb, pf100kb, pf200kb, pf300kb);

function INVBitmap.AsBmpStr                                    : string;
function INVBitmap.AsPngStr (format: TPngFormat = pf256Colors) : string;

function INVBitmap.SaveBmp (bmpFile: UnicodeString                                  ) : boolean;
function INVBitmap.SavePng (pngFile: UnicodeString; format: TPngFormat = pf256Colors) : boolean;

// Example: