public static extern FIBITMAP Dither(FIBITMAP dib, FREE_IMAGE_DITHER algorithm);
public static extern FIBITMAP Dither(FIBITMAP dib, FREE_IMAGE_DITHER algorithm);
public static extern uint Dither(uint dib, FREE_IMAGE_DITHER algorithm);
private static extern FIBITMAP DitherWindows(FIBITMAP dib, FREE_IMAGE_DITHER algorithm);
private static extern FIBITMAP DitherLinux(FIBITMAP dib, FREE_IMAGE_DITHER algorithm);
/// <summary>
/// Converts a FreeImage bitmap from one color depth to another.
/// If the conversion fails the original FreeImage bitmap is returned.
/// </summary>
/// <param name="dib">Handle to a FreeImage bitmap.</param>
/// <param name="conversion">The desired output format.</param>
/// <param name="ditherMethod">Dither algorithm when converting with
/// <see cref="FREE_IMAGE_COLOR_DEPTH.FICD_01_BPP_DITHER"/>.</param>
/// <param name="unloadSource">When true the structure will be unloaded on success.</param>
/// <returns>Handle to a FreeImage bitmap.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="dib"/> is null.</exception>
public static FIBITMAP ConvertColorDepth(
FIBITMAP dib,
FREE_IMAGE_COLOR_DEPTH conversion,
FREE_IMAGE_DITHER ditherMethod,
bool unloadSource)
{
return ConvertColorDepth(
dib,
conversion,
128,
ditherMethod,
FREE_IMAGE_QUANTIZE.FIQ_WUQUANT,
unloadSource);
}
/// <summary>
/// Converts a FreeImage bitmap from one color depth to another.
/// If the conversion fails the original FreeImage bitmap is returned.
/// </summary>
/// <param name="dib">Handle to a FreeImage bitmap.</param>
/// <param name="conversion">The desired output format.</param>
/// <param name="threshold">Threshold value when converting with
/// <see cref="FREE_IMAGE_COLOR_DEPTH.FICD_01_BPP_THRESHOLD"/>.</param>
/// <param name="ditherMethod">Dither algorithm when converting with
/// <see cref="FREE_IMAGE_COLOR_DEPTH.FICD_01_BPP_DITHER"/>.</param>
/// <param name="quantizationMethod">The quantization algorithm for conversion to 8-bit color depth.</param>
/// <param name="unloadSource">When true the structure will be unloaded on success.</param>
/// <returns>Handle to a FreeImage bitmap.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="dib"/> is null.</exception>
internal static FIBITMAP ConvertColorDepth(
FIBITMAP dib,
FREE_IMAGE_COLOR_DEPTH conversion,
byte threshold,
FREE_IMAGE_DITHER ditherMethod,
FREE_IMAGE_QUANTIZE quantizationMethod,
bool unloadSource)
{
if (dib.IsNull)
{
throw new ArgumentNullException("dib");
}
FIBITMAP result = 0;
FIBITMAP dibTemp = 0;
uint bpp = GetBPP(dib);
bool reorderPalette = ((conversion & FREE_IMAGE_COLOR_DEPTH.FICD_REORDER_PALETTE) > 0);
bool forceGreyscale = ((conversion & FREE_IMAGE_COLOR_DEPTH.FICD_FORCE_GREYSCALE) > 0);
switch (conversion & (FREE_IMAGE_COLOR_DEPTH)0xFF)
{
case FREE_IMAGE_COLOR_DEPTH.FICD_01_BPP_THRESHOLD:
if (bpp != 1)
{
result = Threshold(dib, threshold);
}
else
{
bool isGreyscale = IsGreyscaleImage(dib);
if ((forceGreyscale && (!isGreyscale)) ||
(reorderPalette && isGreyscale))
{
result = Threshold(dib, threshold);
}
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_01_BPP_DITHER:
if (bpp != 1)
{
result = Dither(dib, ditherMethod);
}
else
{
bool isGreyscale = IsGreyscaleImage(dib);
if ((forceGreyscale && (!isGreyscale)) ||
(reorderPalette && isGreyscale))
{
result = Dither(dib, ditherMethod);
}
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_04_BPP:
if (bpp != 4)
{
// Special case when 1bpp and FIC_PALETTE
if (forceGreyscale && (bpp == 1) && (GetColorType(dib) == FREE_IMAGE_COLOR_TYPE.FIC_PALETTE))
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo4Bits(dibTemp);
Unload(dibTemp);
}
// All other cases are converted directly
else
{
result = ConvertTo4Bits(dib);
}
}
else
{
bool isGreyscale = IsGreyscaleImage(dib);
if ((forceGreyscale && (!isGreyscale)) ||
(reorderPalette && isGreyscale))
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo4Bits(dibTemp);
Unload(dibTemp);
}
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_08_BPP:
if (bpp != 8)
{
if (forceGreyscale)
{
result = ConvertToGreyscale(dib);
}
else
{
dibTemp = ConvertTo24Bits(dib);
result = ColorQuantize(dibTemp, quantizationMethod);
Unload(dibTemp);
}
}
else
{
bool isGreyscale = IsGreyscaleImage(dib);
if ((forceGreyscale && (!isGreyscale)) || (reorderPalette && isGreyscale))
{
result = ConvertToGreyscale(dib);
}
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_16_BPP_555:
if (forceGreyscale)
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo16Bits555(dibTemp);
Unload(dibTemp);
}
else if (bpp != 16 || GetRedMask(dib) != FI16_555_RED_MASK || GetGreenMask(dib) != FI16_555_GREEN_MASK || GetBlueMask(dib) != FI16_555_BLUE_MASK)
{
result = ConvertTo16Bits555(dib);
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_16_BPP:
if (forceGreyscale)
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo16Bits565(dibTemp);
Unload(dibTemp);
}
else if (bpp != 16 || GetRedMask(dib) != FI16_565_RED_MASK || GetGreenMask(dib) != FI16_565_GREEN_MASK || GetBlueMask(dib) != FI16_565_BLUE_MASK)
{
result = ConvertTo16Bits565(dib);
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_24_BPP:
if (forceGreyscale)
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo24Bits(dibTemp);
Unload(dibTemp);
}
else if (bpp != 24)
{
result = ConvertTo24Bits(dib);
}
break;
case FREE_IMAGE_COLOR_DEPTH.FICD_32_BPP:
if (forceGreyscale)
{
dibTemp = ConvertToGreyscale(dib);
result = ConvertTo32Bits(dibTemp);
Unload(dibTemp);
}
else if (bpp != 32)
{
result = ConvertTo32Bits(dib);
}
break;
}
if (result.IsNull)
{
return dib;
}
if (unloadSource)
{
Unload(dib);
}
return result;
}