internal static async Task <DitherResult> ditherFile(StorageFile file, uint outputWidth, uint outputHeight)
{
int pointCount = 0;
dithermode dm = dithermode.SierraLite;
DitherResult result = new DitherResult();
errorTable = new float[outputWidth * outputHeight];
using (IRandomAccessStream stream = await file.OpenReadAsync())
{
var decoder = await BitmapDecoder.CreateAsync(stream);
var bitmapTransform = new BitmapTransform
{
ScaledWidth = outputWidth,
ScaledHeight = outputHeight
};
var thumbnailColorProvider = await decoder.GetPixelDataAsync(
BitmapPixelFormat.Rgba8,
BitmapAlphaMode.Straight,
bitmapTransform,
ExifOrientationMode.IgnoreExifOrientation,
ColorManagementMode.DoNotColorManage);
var thumbnailColorArray = thumbnailColorProvider.DetachPixelData();
result.width = outputWidth;
result.height = outputHeight;
var thumbnailBWArray = new byte[result.width * result.height];
var thumbnailDitheredArray = new byte[result.width * result.height];
// First Pass, average each triad
for (int i = 0; i < thumbnailBWArray.Length; i++)
{
var r = thumbnailColorArray[i * 4 + 0];
var g = thumbnailColorArray[i * 4 + 1];
var b = thumbnailColorArray[i * 4 + 2];
thumbnailBWArray[i] = getLuminance(r, g, b);
}
int newValue;
float error;
for (var pass = 0; pass < 1; pass++)
{
for (int x = 0; x < result.width; x++)
{
for (int y = 0; y < result.height; y++)
{
int index = y * (int)result.width + x;
newValue = thumbnailBWArray[index] + (int)errorTable[index];
if (newValue >= kBWThreshold)
{
// Set white
error = newValue - 255;
thumbnailDitheredArray[index] = 255;
}
else
{
// Set Black
pointCount++;
error = newValue;
thumbnailDitheredArray[index] = 0;
}
switch (dm)
{
case dithermode.FloydSteinberg:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 7 / 16);
}
if (y + 1 < result.height)
{
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 3 / 16);
}
errorTable[index + result.width] += (error * 5 / 16);
if (x + 1 < result.width)
{
errorTable[index + result.width + 1] += (error * 1 / 16);
}
}
}
break;
case dithermode.Sierra2:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 4 / 16);
}
if (x + 2 < result.width)
{
errorTable[index + 2] += (error * 3 / 16);
}
if (y + 1 < result.height)
{
if (x - 2 >= 0)
{
errorTable[index + result.width - 2] += (error * 1 / 16);
}
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 2 / 16);
}
errorTable[index + result.width] += (error * 3 / 16);
if (x + 1 < result.width)
{
errorTable[index + result.width + 1] += (error * 2 / 16);
}
if (x + 2 < result.width)
{
errorTable[index + result.width + 2] += (error * 1 / 16);
}
}
}
break;
case dithermode.SierraLite:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 2 / 4);
}
if (y + 1 < result.height)
{
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 1 / 4);
}
errorTable[index + result.width] += (error * 1 / 4);
}
}
break;
}
}
}
}
Debug.WriteLine("Point count: " + pointCount);
result.pixels = thumbnailDitheredArray;
return(result);
}
}
internal static async Task<DitherResult> ditherFile(StorageFile file, uint outputWidth, uint outputHeight)
{
int pointCount = 0;
dithermode dm = dithermode.SierraLite;
DitherResult result = new DitherResult();
errorTable = new float[outputWidth * outputHeight];
using (IRandomAccessStream stream = await file.OpenReadAsync())
{
var decoder = await BitmapDecoder.CreateAsync(stream);
var bitmapTransform = new BitmapTransform
{
ScaledWidth = outputWidth,
ScaledHeight = outputHeight
};
var thumbnailColorProvider = await decoder.GetPixelDataAsync(
BitmapPixelFormat.Rgba8,
BitmapAlphaMode.Straight,
bitmapTransform,
ExifOrientationMode.IgnoreExifOrientation,
ColorManagementMode.DoNotColorManage);
var thumbnailColorArray = thumbnailColorProvider.DetachPixelData();
result.width = outputWidth;
result.height = outputHeight;
var thumbnailBWArray = new byte[result.width * result.height];
var thumbnailDitheredArray = new byte[result.width * result.height];
// First Pass, average each triad
for (int i = 0; i < thumbnailBWArray.Length; i++)
{
var r = thumbnailColorArray[i * 4 + 0];
var g = thumbnailColorArray[i * 4 + 1];
var b = thumbnailColorArray[i * 4 + 2];
thumbnailBWArray[i] = getLuminance(r, g, b);
}
int newValue;
float error;
for (var pass = 0; pass < 1; pass++)
{
for (int x = 0; x < result.width; x++)
{
for (int y = 0; y < result.height; y++)
{
int index = y * (int)result.width + x;
newValue = thumbnailBWArray[index] + (int)errorTable[index];
if (newValue >= kBWThreshold)
{
// Set white
error = newValue - 255;
thumbnailDitheredArray[index] = 255;
}
else
{
// Set Black
pointCount++;
error = newValue;
thumbnailDitheredArray[index] = 0;
}
switch (dm)
{
case dithermode.FloydSteinberg:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 7 / 16);
}
if (y + 1 < result.height)
{
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 3 / 16);
}
errorTable[index + result.width] += (error * 5 / 16);
if (x + 1 < result.width)
{
errorTable[index + result.width + 1] += (error * 1 / 16);
}
}
}
break;
case dithermode.Sierra2:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 4 / 16);
}
if (x + 2 < result.width)
{
errorTable[index + 2] += (error * 3 / 16);
}
if (y + 1 < result.height)
{
if (x - 2 >= 0)
{
errorTable[index + result.width - 2] += (error * 1 / 16);
}
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 2 / 16);
}
errorTable[index + result.width] += (error * 3 / 16);
if (x + 1 < result.width)
{
errorTable[index + result.width + 1] += (error * 2 / 16);
}
if (x + 2 < result.width)
{
errorTable[index + result.width + 2] += (error * 1 / 16);
}
}
}
break;
case dithermode.SierraLite:
{
if (x + 1 < result.width)
{
errorTable[index + 1] += (error * 2 / 4);
}
if (y + 1 < result.height)
{
if (x - 1 >= 0)
{
errorTable[index + result.width - 1] += (error * 1 / 4);
}
errorTable[index + result.width] += (error * 1 / 4);
}
}
break;
}
}
}
}
Debug.WriteLine("Point count: " + pointCount);
result.pixels = thumbnailDitheredArray;
return result;
}
}