public static string SaveSmallestBitmap(Bitmap sourceImage, ScanBitDepth bitDepth, bool highQuality, int quality, out ImageFormat imageFormat)
{
// Store the image in as little space as possible
if (sourceImage.PixelFormat == PixelFormat.Format1bppIndexed)
{
// Already encoded as 1-bit
imageFormat = ImageFormat.Png;
return(EncodePng(sourceImage));
}
else if (bitDepth == ScanBitDepth.BlackWhite)
{
// Convert to a 1-bit bitmap before saving to help compression
// This is lossless and takes up minimal storage (best of both worlds), so highQuality is irrelevant
using (var bitmap = BitmapHelper.CopyToBpp(sourceImage, 1))
{
imageFormat = ImageFormat.Png;
return(EncodePng(bitmap));
}
// Note that if a black and white image comes from native WIA, bitDepth is unknown,
// so the image will be png-encoded below instead of using a 1-bit bitmap
}
else if (highQuality)
{
// Store as PNG
// Lossless, but some images (color/grayscale) take up lots of storage
imageFormat = ImageFormat.Png;
return(EncodePng(sourceImage));
}
else if (Equals(sourceImage.RawFormat, ImageFormat.Jpeg))
{
// Store as JPEG
// Since the image was originally in JPEG format, PNG is unlikely to have size benefits
imageFormat = ImageFormat.Jpeg;
return(EncodeJpeg(sourceImage, quality));
}
else
{
// Store as PNG/JPEG depending on which is smaller
var pngEncoded = EncodePng(sourceImage);
var jpegEncoded = EncodeJpeg(sourceImage, quality);
if (new FileInfo(pngEncoded).Length <= new FileInfo(jpegEncoded).Length)
{
// Probably a black and white image (from native WIA, so bitDepth is unknown), which PNG compresses well vs. JPEG
File.Delete(jpegEncoded);
imageFormat = ImageFormat.Png;
return(pngEncoded);
}
else
{
// Probably a color or grayscale image, which JPEG compresses well vs. PNG
File.Delete(pngEncoded);
imageFormat = ImageFormat.Jpeg;
return(jpegEncoded);
}
}
}
public bool IsBlank(Bitmap bitmap, int whiteThresholdNorm, int coverageThresholdNorm)
{
if (bitmap.PixelFormat == PixelFormat.Format1bppIndexed)
{
using (var bitmap2 = BitmapHelper.CopyToBpp(bitmap, 8))
{
return(IsBlankRgb(bitmap2, whiteThresholdNorm, coverageThresholdNorm));
}
}
return(bitmap.PixelFormat == PixelFormat.Format24bppRgb && IsBlankRgb(bitmap, whiteThresholdNorm, coverageThresholdNorm));
}
public static void GetSmallestBitmap(Bitmap sourceImage, ScanBitDepth bitDepth, bool highQuality, out Bitmap bitmap, out MemoryStream encodedBitmap, out ImageFormat imageFormat)
{
// Defaults for out arguments
bitmap = null;
encodedBitmap = null;
imageFormat = ImageFormat.Png;
// Store the image in as little space as possible
if (bitDepth == ScanBitDepth.BlackWhite)
{
// Store as a 1-bit bitmap
// This is lossless and takes up minimal storage (best of both worlds), so highQuality is irrelevant
bitmap = (Bitmap)BitmapHelper.CopyToBpp(sourceImage, 1).Clone();
// Note that if a black and white image comes from native WIA, bitDepth is unknown,
// so the image will be png-encoded below instead of using a 1-bit bitmap
}
else if (highQuality)
{
// Store as PNG
// Lossless, but some images (color/grayscale) take up lots of storage
encodedBitmap = EncodeBitmap(sourceImage, ImageFormat.Png);
}
else
{
// Store as PNG/JPEG depending on which is smaller
var pngEncoded = EncodeBitmap(sourceImage, ImageFormat.Png);
var jpegEncoded = EncodeBitmap(sourceImage, ImageFormat.Jpeg);
if (pngEncoded.Length <= jpegEncoded.Length)
{
// Probably a black and white image (from native WIA, so bitDepth is unknown), which PNG compresses well vs. JPEG
encodedBitmap = pngEncoded;
jpegEncoded.Dispose();
}
else
{
// Probably a color or grayscale image, which JPEG compresses well vs. PNG
encodedBitmap = jpegEncoded;
pngEncoded.Dispose();
imageFormat = ImageFormat.Jpeg;
}
}
}