BITMAPFILEHEADER.bfOffBits is ignored

[hughbe]

Cause of issue in #276 (review)

[filipnavara]

Makes me wonder what you can do with hacks where the bits would intentionally overlap with the bitmap header... or if you can embed custom metadata between the official headers and the bitmap data.

[filipnavara]

Also, biClrUsed is ignored as well.

[hughbe]

Makes me wonder what you can do with hacks where the bits would intentionally overlap with the bitmap header... or if you can embed custom metadata between the official headers and the bitmap data.

If the bits intentionally overlap with the bitmap header, the offset is ignored (in GDI+)

or if you can embed custom metadata between the official headers and the bitmap data.

Yes you can!

E.g.

BYTE validOffset2OS2Indexed[] = {
    // -- BITMAPFILEHEADER -- //
    /* Signature */ 0x42, 0x4D,
    /* File Size */ 0x24, 0x00, 0x00, 0x00,
    /* Reserved */	0x00, 0x00, 0x00, 0x00,
    /* Offset */    0x2E, 0x00, 0x00, 0x00,

    // -- BITMAPCOREHEADER -- //
    /* Size */      0x0C, 0x00, 0x00, 0x00,
    /* Width */     0x01, 0x00,
    /* Height */    0x01, 0x00,
    /* Planes */    0x01, 0x00,
    /* Bit Count */ 0x01, 0x00,

    // -- Color Palette -- //
    0xFF, 0x00, 0x00, 0x00, 0xFF, 0x0,

    // -- Padding -- //
    'H', 'i', 'd', 'd', 'e', 'n', ' ', 'M', 'e', 's', 's', 'a', 'g', 'e',

    // -- Image Data -- //
    0x80, 0x00, 0x00, 0x00
};

createFileSuccessDispose (validOffset2OS2Indexed, PixelFormat1bppIndexed, 1, 1, bmpFlags, FALSE);
ARGB expectedPixels[] = {0xFF00FF00};
verifyPixels (image, expectedPixels);
ARGB expectedPalette[] = {0xFF0000FF, 0xFF00FF00};
verifyPalette (image, 0, expectedPalette);
GdipDisposeImage (image);