Converts AutoCAD block PreviewIcon bytes to a browser-displayable BMP data URL.
PreviewIcon data is typically a Device-Independent Bitmap (DIB): a memory copy
of BITMAPINFO
followed by pixel bits (DXF BLOCK_RECORD group 310). A full BMP file also has a
14-byte BITMAPFILEHEADER; this helper prepends that header when needed.
Parameters
data: undefined|null|Uint8Array
Raw PreviewIcon bytes, or an empty buffer when none exist.
Returns string|undefined
A data:image/bmp;base64,... URL, or undefined when the payload is empty/invalid.
Converts AutoCAD block PreviewIcon bytes to a browser-displayable BMP data URL.
PreviewIcon data is typically a Device-Independent Bitmap (DIB): a memory copy of BITMAPINFO followed by pixel bits (DXF BLOCK_RECORD group 310). A full BMP file also has a 14-byte BITMAPFILEHEADER; this helper prepends that header when needed.