BITMAPINFOHEADER

pub const BITMAPINFOHEADER = extern struct

File

Code

pub const BITMAPINFOHEADER = extern struct {
    bcSize: u32,
    biWidth: i32,
    biHeight: i32,
    biPlanes: u16,
    biBitCount: u16,
    biCompression: u32,
    biSizeImage: u32,
    biXPelsPerMeter: i32,
    biYPelsPerMeter: i32,
    biClrUsed: u32,
    biClrImportant: u32,

    /// Returns error.TooManyColorsInPalette if the number of colors specified
    /// exceeds the number of possible colors referenced in the pixel data (i.e.
    /// if 1 bit is used per pixel, then the color table can't have more than 2 colors
    /// since any more couldn't possibly be indexed in the pixel data)
    ///
    /// Returns error.InvalidBitsPerPixel if the bit depth is not 1, 4, 8, 16, 24, or 32.
    pub fn numColorsInTable(self: BITMAPINFOHEADER) !u32 {
        switch (self.biBitCount) {
            inline 1, 4, 8 => |bit_count| switch (self.biClrUsed) {
                // > If biClrUsed is zero, the array contains the maximum number of
                // > colors for the given bitdepth; that is, 2^biBitCount colors
                0 => return 1 << bit_count,
                // > If biClrUsed is nonzero and the biBitCount member is less than 16,
                // > the biClrUsed member specifies the actual number of colors the
                // > graphics engine or device driver accesses.
                else => {
                    const max_colors = 1 << bit_count;
                    if (self.biClrUsed > max_colors) {
                        return error.TooManyColorsInPalette;
                    }
                    return self.biClrUsed;
                },
            },
            // > If biBitCount is 16 or greater, the biClrUsed member specifies
            // > the size of the color table used to optimize performance of the
            // > system color palettes.
            //
            // Note: Bit depths >= 16 only use the color table 'for optimizing colors
            // used on palette-based devices', but it still makes sense to limit their
            // colors since the pixel data is still limited to this number of colors
            // (i.e. even though the color table is not indexed by the pixel data,
            // the color table having more colors than the pixel data can represent
            // would never make sense and indicates a malformed bitmap).
            inline 16, 24, 32 => |bit_count| {
                const max_colors = 1 << bit_count;
                if (self.biClrUsed > max_colors) {
                    return error.TooManyColorsInPalette;
                }
                return self.biClrUsed;
            },
            else => return error.InvalidBitsPerPixel,
        }
    }
}