SeeDIB.exe Shows 16 and 32 Bits-Per-Pel Bitmap Formats

SeeDIB.exe is a sample application that demonstrates how to load, display, and save 1, 4, 8, 16, 24, and 32-bits-per-pixel (Device Independent Bitmap (DIB) formats. In addition, SeeDIB.exe demonstrates a simple method of creating an optimized palette for displaying DIBs with more than 8-bits-per-pixel on 8-bits-per-pixel devices.

Note To minimize color loss, SeeDIB uses CreateDIBSection() to do conversions between uncompressed DIBs which have more than 8-bits-per- pixel. This function is not available on Windows NT 3.1.

The following file is available for download from the Microsoft Download Center:
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file. For DIBs, the 16 and 32-bit formats contain three DWORD masks in the bmiColors member of the BITMAPINFO structure. These masks specify which bits in the pel correspond to which color.

The three masks must have contiguous bits, and their order is assumed to be R, G, B (high bits to low bits). The order of the three masks in the color table must also be first red, then green, then blue (RGB). In this manner, the programmer can specify a mask indicating how many shades of each RGB color will be available for bitmaps created with CreateDIBitmap(). For 16-bits-per-pixel DIBs, CreateDIBitmap() defaults to the RGB555 format. For 32-bits-per-pixel DIBs, CreateDIBitmap() defaults to an RGB888 format.

NOTE: The DIB engine in Windows 95 supports only RGB555 and RGB565 for 16-bit DIBs and only RGB888 for 32-bit DIBs.

Example

The RGB555 format masks would look like the following example: NOTE: For 16 bits-per-pel, the upper half of the DWORDs are always zeroed.

The RGB888 format masks would look like the following example:

Usage

When using 16 and 32-bit formats, there are also certain fields of the BITMAPINFOHEADER structure that must be set to the correct values:

1. The biCompression member must be set to either BI_RGB or BI_BITFIELDS. Using BI-RGB indicates that no bit masks are included in the color table and that the default (RGB555 for 16bpp and RGB888 for 32bpp) format is implied. Using BI_BITFIELDS indicates that there are masks (bit fields) specified in the color table.
2. As with 24-bits-per-pixel formats, the biClrUsed member specifies the size of the color table used to optimize performance of Windows color palettes. If the biCompression is set to BI_BITFIELDS, then the optimal color palette starts immediately following the three DWORD masks. Note that an optimal color palette is optional and many applications will ignore it.

Windows 95

In Windows 95, if the BI_BITFIELDS flag is set, then a color mask must be specified and it must be one of the following: User-defined color masks are not available under Windows 95.