public void NestedView_2D()
{
var data = new ArraySlice <int>(new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }).Reshape(2, 10);
//>>> x = np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
//>>> x = x.reshape(2, 10)
//>>> x
//array([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
// [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]])
// return identical view
var identical = new ArraySlice <int>(data, ":");
Assert.AreEqual(new Shape(2, 10), identical.Shape);
//>>> x[:, 1:9]
//array([[1, 2, 3, 4, 5, 6, 7, 8],
// [1, 2, 3, 4, 5, 6, 7, 8]])
var view1 = new ArraySlice <int>(identical, ":,1:9");
Assert.AreEqual(new Shape(2, 8), view1.Shape);
Assert.AreEqual(new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8 }, view1);
//>>> x[:, 1:9][:,::- 2]
//array([[8, 6, 4, 2],
// [8, 6, 4, 2]])
var view2 = new ArraySlice <int>(view1, ":,::-2");
Assert.AreEqual(new Shape(2, 4), view2.Shape);
Assert.AreEqual(new int[] { 8, 6, 4, 2, 8, 6, 4, 2 }, view2);
//>>> x[:, 1:9][:,::- 2][:,::- 3]
//array([[2, 8],
// [2, 8]])
var view3 = new ArraySlice <int>(view2, ":,::-3");
Assert.AreEqual(new Shape(2, 2), view3.Shape);
Assert.AreEqual(new int[] { 2, 8, 2, 8 }, view3);
// all must see the same modifications, no matter if original or any view is modified
// modify original
data.SetValues(0, new int[] { 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, 0, -1, -2, -3, -4, -5, -6, -7, -8, -9 });
Assert.AreEqual(new int[] { -1, -2, -3, -4, -5, -6, -7, -8, -1, -2, -3, -4, -5, -6, -7, -8 }, view1);
Assert.AreEqual(new int[] { -8, -6, -4, -2, -8, -6, -4, -2 }, view2);
Assert.AreEqual(new int[] { -2, -8, -2, -8 }, view3);
// modify views
view1[0, 7] = 88;
view1[1, 7] = 888;
Assert.AreEqual(new int[] { 0, -1, -2, -3, -4, -5, -6, -7, 88, -9, 0, -1, -2, -3, -4, -5, -6, -7, 888, -9 },
data);
Assert.AreEqual(new int[] { -1, -2, -3, -4, -5, -6, -7, 88, -1, -2, -3, -4, -5, -6, -7, 888 },
view1);
Assert.AreEqual(new int[] { 88, -6, -4, -2, 888, -6, -4, -2 }, view2);
Assert.AreEqual(new int[] { -2, 88, -2, 888 }, view3);
view3[0, 0] = 22;
view3[1, 0] = 222;
Assert.AreEqual(new int[] { 0, -1, 22, -3, -4, -5, -6, -7, 88, -9, 0, -1, 222, -3, -4, -5, -6, -7, 888, -9 },
data);
Assert.AreEqual(new int[] { -1, 22, -3, -4, -5, -6, -7, 88, -1, 222, -3, -4, -5, -6, -7, 888 },
view1);
Assert.AreEqual(new int[] { 88, -6, -4, 22, 888, -6, -4, 222 }, view2);
Assert.AreEqual(new int[] { 22, 88, 222, 888 }, view3);
}
public void NestedView_1D()
{
var data = new ArraySlice <int>(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
// return identical view
var identical = new ArraySlice <int>(data, ":");
Assert.AreEqual(new Shape(10), identical.Shape);
var view1 = new ArraySlice <int>(identical, "1:9");
Assert.AreEqual(new Shape(8), view1.Shape);
Assert.AreEqual(new int[] { 1, 2, 3, 4, 5, 6, 7, 8, }, view1);
var view2 = new ArraySlice <int>(view1, "::-2");
Assert.AreEqual(new Shape(4), view2.Shape);
Assert.AreEqual(new int[] { 8, 6, 4, 2, }, view2);
var view3 = new ArraySlice <int>(view2, "::-3");
Assert.AreEqual(new Shape(2), view3.Shape);
Assert.AreEqual(new int[] { 2, 8 }, view3);
// all must see the same modifications, no matter if original or any view is modified
// modify original
data.SetValues(
0, new int[] { 0, -1, -2, -3, -4, -5, -6, -7, -8, -9 });
Assert.AreEqual(new int[] { -1, -2, -3, -4, -5, -6, -7, -8, }, view1);
Assert.AreEqual(new int[] { -8, -6, -4, -2, }, view2);
Assert.AreEqual(new int[] { -2, -8 }, view3);
// modify views
view1[7] = 88;
Assert.AreEqual(new int[] { 0, -1, -2, -3, -4, -5, -6, -7, 88, -9 }, data);
Assert.AreEqual(new int[] { -1, -2, -3, -4, -5, -6, -7, 88, }, view1);
Assert.AreEqual(new int[] { 88, -6, -4, -2, }, view2);
Assert.AreEqual(new int[] { -2, 88 }, view3);
view3[0] = 22;
Assert.AreEqual(new int[] { 0, -1, 22, -3, -4, -5, -6, -7, 88, -9 }, data);
Assert.AreEqual(new int[] { -1, 22, -3, -4, -5, -6, -7, 88, }, view1);
Assert.AreEqual(new int[] { 88, -6, -4, 22, }, view2);
Assert.AreEqual(new int[] { 22, 88 }, view3);
}
public void ImageProcessingExample()
{
var width = 4; // px
var height = 4; // px
var bytes_per_pixel = 3; // r, g, b
// note that Slice and Dice uses the row major coordinate system like numpy
// so the coordinate order is y, x, color in this example
var shape = new Shape(height, width, bytes_per_pixel);
// create the raw pixel data using Shape.Size to calculate how long the array
// must be to hold a 3D volume of h x w x byte_per_pixel
var raw_bytes = new byte[shape.Size];
var image = new ArraySlice <byte>(raw_bytes, shape);
// we can now access single pixel values by coordinates
// get the three bytes for the pixel at the upper right corner
// as ArraySlice<T> without copying any data!
var pixel = image.GetSlice("0, 3");
Console.WriteLine("pixel: " + pixel); // prints: pixel: [0, 0, 0]
// set the pixel to white
image.SetValues(new int[] { 0, 3 }, new byte[] { 255, 255, 255 });
// get the 2 by 2 pixel patch at the center and color it green without copying any data:
var patch = image.GetSlice("1:3, 1:3, 1"); // this gets only the green channel
// note how we can now use relative coordinates in the patch
// since this is a slice of the green channel we can directly set the green byte at location (y,x)
for (int y = 0; y < 2; y++)
{
for (int x = 0; x < 2; x++)
{
patch[y, x] = 255;
}
}
// print the bitmap out row by row like this (black = '#', white = ' ', green= 'o')
// obviously by using slicing this is a no-brainer
for (int y = 0; y < height; y++)
{
Console.Write("|");
// Slice.Index gives us a slice-definition for a row at index y.
// You could also use image.GetSlice($"{y}")
var row = image.GetSlice(Slice.Index(y));
for (int x = 0; x < width; x++)
{
var red = row[x, 0];
var green = row[x, 1];
if (red == 0 && green == 0)
{
// must be black
Console.Write("#");
continue;
}
if (red == 255 && green == 255)
{
// must be white
Console.Write(" ");
continue;
}
if (green == 255)
{
Console.Write("o");
}
}
// at the end of the row, break the line
Console.WriteLine("|");
}
}