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@@ -61,4 +61,107 @@ public class SixelEncoderTests
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Assert.Equal (expected, result);
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}
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+
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+ [Fact]
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+ public void EncodeSixel_12x12GridPattern3x3_ReturnsExpectedSixel ()
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+ {
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+ /*
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+ * Each block is a 3x3 square, alternating black and white.
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+ * The pattern alternates between rows, creating a checkerboard.
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+ * We have 4 blocks per row, and this repeats over 12x12 pixels.
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+
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+ ███...███...
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+ ███...███...
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+ ███...███...
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+ ...███...███
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+ ...███...███
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+ ...███...███
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+ ███...███...
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+ ███...███...
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+ ███...███...
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+ ...███...███
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+ ...███...███
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+ ...███...███
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+
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+ Because we are dealing with sixels (drawing 6 rows at once) we will
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+ see 2 bands being drawn. We will also see how we have to 'go back over'
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+ the current line after drawing the black (so we can draw the white).
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+
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+ */
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+
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+
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+ var expected = "\u001bP" + // Start sixel sequence
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+ "0;0;0" + // Defaults for aspect ratio and grid size
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+ "q" + // Signals beginning of sixel image data
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+ "\"1;1;12;2" + // no scaling factors (1x1) and filling 12px width with 2 'sixel' height = 12 px high
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+
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+ /*
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+ * Definition of the color palette
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+ */
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+ "#0;2;0;0;0" + // Black color definition (index 0: RGB 0,0,0)
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+ "#1;2;100;100;100" + // White color definition (index 1: RGB 100,100,100)
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+
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+ /*
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+ * Start of the Pixel data
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+ *
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+ * Lets consider only the first 6 pixel (vertically). We have to fill the top 3 black and bottom 3 white.
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+ * So we need to select black and fill 000111. To convert this into a character we must +63 and convert to ASCII
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+ * Later on we will also need to select white and fill the inverse i.e. 111000.
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+ *
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+ * 111000 (binary) → w (ASCII 119).
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+ * 000111 (binary) → F (ASCII 70).
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+ *
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+ * Therefore the lines become
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+ *
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+ * #0 (Select black)
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+ * FFF (fill first 3 pixels horizontally - and top half of band black)
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+ * www (fill next 3 pixels horizontally - bottom half of band black)
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+ * FFFwww (as above to finish the line
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+ *
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+ * Next we must go back and fill the white (on the same band)
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+ * #1 (Select white)
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+ *
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+ */
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+ "#0FFFwwwFFFwww$" + // First pass of top band (Filling black)
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+ "#1wwwFFFwwwFFF$-" + // Second pass of top band (Filling white)
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+
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+ // Sequence repeats exactly the same because top band is actually identical pixels to bottom band
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+ "#0FFFwwwFFFwww$" + // First pass of bottom band (Filling white)
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+ "#1wwwFFFwwwFFF$" + // Second pass of bottom band (Filling black)
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+
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+ "\u001b\\"; // End sixel sequence
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+
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+ // Arrange: Create a 12x12 bitmap with a 3x3 checkerboard pattern
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+ var pixels = new Color [12, 12];
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+ for (int y = 0; y < 12; y++)
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+ {
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+ for (int x = 0; x < 12; x++)
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+ {
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+ // Create a 3x3 checkerboard by alternating the color based on pixel coordinates
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+ if (((x / 3) + (y / 3)) % 2 == 0)
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+ {
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+ pixels [x, y] = new Color (0, 0, 0); // Black
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+ }
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+ else
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+ {
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+ pixels [x, y] = new Color (255, 255, 255); // White
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+ }
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+ }
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+ }
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+
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+ // Act: Encode the image
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+ var encoder = new SixelEncoder (); // Assuming SixelEncoder is the class that contains the EncodeSixel method
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+ string result = encoder.EncodeSixel (pixels);
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+
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+ // We should have only black and white in the palette
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+ Assert.Equal (2, encoder.Quantizer.Palette.Count);
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+ Color black = encoder.Quantizer.Palette.ElementAt (0);
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+ Color white = encoder.Quantizer.Palette.ElementAt(1);
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+
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+ Assert.Equal (new Color (0, 0, 0), black);
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+ Assert.Equal (new Color (255, 255, 255), white);
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+
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+ // Compare the generated SIXEL string with the expected one
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+ Assert.Equal (expected, result);
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+ }
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}
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tznind