Synopsis:
This sample project demonstrates how to print a bitmap by using the StretchDIBits
function.
Abstract:
As I mentioned in Chapter 6, a color device-dependent bitmap (DDB) is--as
it's name suggests--a device dependent entity. Recall that the hdc
parameter of the CreateCompatibleBitmap function is your way of
telling the function with which device you want the DDB to be compatible;
in turn, the CreateCompatibleBitmap function will instruct the
corresponding device driver to create the DDB. Because a DDB that's
been created by a specific device is stored in a format known only to that
device, you can use blitting functions--such as BitBlt and StretchBlt--to
render a DDB only to the device with which the DDB is
compatible. For example, if you create a DDB that's compatible with
the screen (say, by passing the CreateCompatibleBitmap function a
handle to the screen's DC or by using the LoadImage function), you
can't use BitBlt or StretchBlt to draw this bitmap to a
printer's device context. This limitation is documented by Microsoft
in the following Knowledge Base article: Q195830-INFO:
Blitting Between DCs for Different Devices Is Unsupported. In
contrast, and as mentioned in Chapter 7, the format of a
device-independent bitmap (DIB) is not device specific. Remember, a
DIB is nothing more than a block of memory that contains a header, a color
table, and an array of pixels. This means that you can safely
transfer a DIB (or a DIB section bitmap) to a printer's device context by
using the StretchDIBits function. This sample project
demonstrates: (1) how to convert a DDB to a DIB; (2) how to convert a DIB
section bitmap to a DIB; and (3) how to use the StretchDIBits
function to send a DIB to the printer. This sample project also
demonstrates how to work around the limitations of the StretchDIBits
function on Windows 9x/Me-based systems by using a technique called
banding.
Keywords:
Device-dependent bitmap, Device-independent bitmap, DIB section bitmap,
DDB, DIB, StretchDIBits, GetDIBits.
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