/// <summary>
/// Erases paint on a pbgra32 WriteableBitmap
/// </summary>
/// <param name="bmp">The bitmap to modify</param>
/// <param name="from">The starting point of the stroke</param>
/// <param name="to">The end point of the stroke</param>
/// <param name="size">The stroke size</param>
public static unsafe void Erase(WriteableBitmap bmp, Point from, Point to, int size)
{
if (bmp == null) return;
bmp.Lock();
// Intermediate storage of the square of the size
int sizesize = size * size;
// Create a line segment representation to compare distance to
LineSegment linesegment = new LineSegment(from, to);
// Get a bounding box for the line segment
BoundingBox bitmapbounds = new BoundingBox();
BoundingBox segmentbounds = new BoundingBox();
bitmapbounds.AddPoint(0, 0, 0);
bitmapbounds.AddPoint(bmp.PixelWidth - 1, bmp.PixelHeight - 1, 0);
segmentbounds.AddPoint((int)from.X, (int)from.Y, size);
segmentbounds.AddPoint((int)to.X, (int)to.Y, size);
segmentbounds.Clip(bitmapbounds);
// Get a pointer to the back buffer (we use an int pointer here, since we can safely assume a 32-bit pixel format)
Int32* start = (Int32*)bmp.BackBuffer.ToPointer();
// Move the starting pixel to the x offset
start += segmentbounds.Left;
// Loop through the relevant portion of the image and figure out which pixels need to be erased
for (int y = segmentbounds.Top; y < segmentbounds.Bottom; y++)
{
Int32* pixel = start + bmp.BackBufferStride / sizeof(Int32) * y;
for (int x = segmentbounds.Left; x < segmentbounds.Right; x++)
{
if (linesegment.DistanceSquared(x, y) <= sizesize)
*pixel = 0;
// Move to the next pixel
pixel++;
}
}
bmp.AddDirtyRect(new Int32Rect(segmentbounds.Left, segmentbounds.Top, segmentbounds.Width, segmentbounds.Height));
bmp.Unlock();
}
/// <summary>
/// Paints on a pbgra32 WriteableBitmap like a paintbrush
/// </summary>
/// <param name="bmp">The bitmap to modify</param>
/// <param name="from">The starting point of the stroke</param>
/// <param name="to">The end point of the stroke</param>
/// <param name="previous">The point prior to the 'from' point, or null</param>
/// <param name="color">The color of the brush</param>
/// <param name="size">The stroke size</param>
public static unsafe void Brush(WriteableBitmap bmp, Point from, Point to, Point? previous, Color color, int size)
{
if (bmp == null) return;
bmp.Lock();
// Intermediate storage of the square of the size
int sizesize = size * size;
uint flatcolor = (uint)((int)color.A << 24) + (uint)((int)color.R << 16) + (uint)((int)color.G << 8) + color.B;
// Create a line segment representation to compare distance to
LineSegment linesegment = new LineSegment(from, to);
// Get a bounding box for the line segment
BoundingBox bitmapbounds = new BoundingBox();
BoundingBox segmentbounds = new BoundingBox();
bitmapbounds.AddPoint(0, 0, 0);
bitmapbounds.AddPoint(bmp.PixelWidth - 1, bmp.PixelHeight - 1, 0);
segmentbounds.AddPoint((int)from.X, (int)from.Y, size);
segmentbounds.AddPoint((int)to.X, (int)to.Y, size);
segmentbounds.Clip(bitmapbounds);
// Get a pointer to the back buffer (we use an int pointer here, since we can safely assume a 32-bit pixel format)
UInt32* start = (UInt32*)bmp.BackBuffer.ToPointer();
// Move the starting pixel to the x offset
start += segmentbounds.Left;
if (previous.HasValue)
{
LineSegment previoussegment = new LineSegment(previous.Value, from);
// Loop through the relevant portion of the image and figure out which pixels need to be erased
for (int y = segmentbounds.Top; y < segmentbounds.Bottom; y++)
{
UInt32* pixel = start + bmp.BackBufferStride / sizeof(UInt32) * y;
for (int x = segmentbounds.Left; x < segmentbounds.Right; x++)
{
if (linesegment.DistanceSquared(x, y) <= sizesize && previoussegment.DistanceSquared(x, y) > sizesize)
{
if (color.A == 255)
*pixel = flatcolor;
else
WriteAlphaBlended(pixel, color);
}
// Move to the next pixel
pixel++;
}
}
}
else
{
// Loop through the relevant portion of the image and figure out which pixels need to be erased
for (int y = segmentbounds.Top; y < segmentbounds.Bottom; y++)
{
UInt32* pixel = start + bmp.BackBufferStride / sizeof(UInt32) * y;
for (int x = segmentbounds.Left; x < segmentbounds.Right; x++)
{
if (linesegment.DistanceSquared(x, y) <= sizesize)
{
if (color.A == 255)
*pixel = flatcolor;
else
WriteAlphaBlended(pixel, color);
}
// Move to the next pixel
pixel++;
}
}
}
bmp.AddDirtyRect(new Int32Rect(segmentbounds.Left, segmentbounds.Top, segmentbounds.Width, segmentbounds.Height));
bmp.Unlock();
}