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Reimplement text contrast using greyscale dilation.

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This commit is contained in:
Paul Chote
2019-12-27 13:26:47 +00:00
committed by Matthias Mailänder
parent 15b2d6b9e0
commit 7611449d3d
1 changed files with 160 additions and 6 deletions
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166
OpenRA.Game/Graphics/SpriteFont.cs
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@@ -25,6 +25,8 @@ namespace OpenRA.Graphics
readonly Func<string, float> lineWidth;
readonly IFont font;
readonly Cache<Pair<char, Color>, GlyphInfo> glyphs;
readonly Cache<Tuple<char, Color, int>, Sprite> contrastGlyphs;
readonly Cache<int, float[]> dilationElements;
float deviceScale;
@@ -40,6 +42,8 @@ namespace OpenRA.Graphics
font = Game.Renderer.CreateFont(data);
glyphs = new Cache<Pair<char, Color>, GlyphInfo>(CreateGlyph, Pair<char, Color>.EqualityComparer);
contrastGlyphs = new Cache<Tuple<char, Color, int>, Sprite>(CreateContrastGlyph);
dilationElements = new Cache<int, float[]>(CreateCircularWeightMap);
// PERF: Cache these delegates for Measure calls.
Func<char, float> characterWidth = character => glyphs[Pair.New(character, Color.White)].Advance;
@@ -55,6 +59,7 @@ namespace OpenRA.Graphics
{
deviceScale = scale;
glyphs.Clear();
contrastGlyphs.Clear();
}
void PrecacheColor(Color c, string name)
@@ -65,6 +70,38 @@ namespace OpenRA.Graphics
throw new InvalidOperationException();
}
void DrawTextContrast(string text, float2 location, Color contrastColor, int contrastOffset)
{
// Offset from the baseline position to the top-left of the glyph for rendering
location += new float2(0, size);
var screenContrast = (int)(contrastOffset * deviceScale);
var p = location;
foreach (var s in text)
{
if (s == '\n')
{
location += new float2(0, size);
p = location;
continue;
}
// Color of source glyph doesn't matter, so use black
var g = glyphs[Pair.New(s, Color.Black)];
if (g.Sprite != null)
{
var contrastSprite = contrastGlyphs[Tuple.Create(s, contrastColor, screenContrast)];
Game.Renderer.RgbaSpriteRenderer.DrawSprite(contrastSprite,
new float2(
(int)Math.Round(p.X * deviceScale + g.Offset.X - screenContrast, 0) / deviceScale,
p.Y + (g.Offset.Y - screenContrast) / deviceScale),
contrastSprite.Size / deviceScale);
}
p += new float2(g.Advance / deviceScale, 0);
}
}
public void DrawText(string text, float2 location, Color c)
{
// Offset from the baseline position to the top-left of the glyph for rendering
@@ -141,12 +178,7 @@ namespace OpenRA.Graphics
public void DrawTextWithContrast(string text, float2 location, Color fg, Color bg, int offset)
{
if (offset > 0)
{
DrawText(text, location + new float2(-offset / deviceScale, 0), bg);
DrawText(text, location + new float2(offset / deviceScale, 0), bg);
DrawText(text, location + new float2(0, -offset / deviceScale), bg);
DrawText(text, location + new float2(0, offset / deviceScale), bg);
}
DrawTextContrast(text, location, bg, offset);
DrawText(text, location, fg);
}
@@ -239,6 +271,128 @@ namespace OpenRA.Graphics
return g;
}
float[] CreateCircularWeightMap(int r)
{
// Create circular weight maps that are used by CreateContrastGlyph for
// both the structuring element and to weight the resulting pixel value.
// The output is a 2 * r + 1 square array giving the pixel intersection
// with a circle of radius (r + 0.5).
//
// Example output for r=1:
// 0.60 1.00 0.60
// 1.00 1.00 1.00
// 0.60 1.00 0.60
//
// Example output for r=3:
// 0.00 0.44 0.80 1.00 0.80 0.44 0.00
// 0.44 1.00 1.00 1.00 1.00 1.00 0.44
// 0.80 1.00 1.00 1.00 1.00 1.00 0.80
// 1.00 1.00 1.00 1.00 1.00 1.00 1.00
// 0.80 1.00 1.00 1.00 1.00 1.00 0.80
// 0.44 1.00 1.00 1.00 1.00 1.00 0.44
// 0.00 0.44 0.80 1.00 0.80 0.44 0.00
var stride = 2 * r + 1;
var elem = new float[stride * stride];
for (var j = 0; j <= 2 * r; j++)
{
for (var i = 0; i <= 2 * r; i++)
{
var di = i - r;
var dj = j - r;
// No intersection with circle
if (di * di + dj * dj > (r + 1) * (r + 1))
continue;
// Fully contained within circle
if (di * di + dj * dj < (r - 1) * (r - 1))
{
elem[j * stride + i] = 1;
continue;
}
// Approximate sub-pixel intersection using a 5x5 grid
for (var jj = 0; jj < 5; jj++)
{
for (var ii = 0; ii < 5; ii++)
{
var si = di - (float)Math.Sign(di) * ii / 5;
var sj = dj - (float)Math.Sign(dj) * jj / 5;
if (si * si + sj * sj <= r * r)
elem[j * stride + i] += 0.04f;
}
}
}
}
return elem;
}
Sprite CreateContrastGlyph(Tuple<char, Color, int> c)
{
// Source glyph color doesn't matter, so use black
var glyph = glyphs[Pair.New(c.Item1, Color.Black)];
var color = c.Item2;
var r = c.Item3;
var size = new Size(glyph.Sprite.Bounds.Width + 2 * r, glyph.Sprite.Bounds.Height + 2 * r);
var s = builder.Allocate(size);
var dest = s.Sheet.GetData();
var destStride = s.Sheet.Size.Width * 4;
var glyphData = glyph.Sprite.Sheet.GetData();
var glyphStride = glyph.Sprite.Sheet.Size.Width * 4;
var glyphBounds = glyph.Sprite.Bounds;
var elem = dilationElements[r];
var elemStride = 2 * r + 1;
// Expand the glyph by applying the greyscale dilation operator to the source glyph's alpha channel
for (var j = 0; j < s.Size.Y; j++)
{
for (var i = 0; i < s.Size.X; i++)
{
// Apply the weight map to the source glyph and find the largest weighted alpha
var first = true;
var alpha = (byte)0;
for (var wj = 0; wj <= 2 * r; wj++)
{
for (var wi = 0; wi <= 2 * r; wi++)
{
// Ignore pixels that are outside the source glyph bounds
var ii = i + wi - 2 * r;
var jj = j + wj - 2 * r;
if (ii < 0 || ii >= glyphBounds.Width || jj < 0 || jj >= glyphBounds.Height)
continue;
// Weighted alpha for this pixel
var weighted = (byte)(elem[wj * elemStride + wi] * glyphData[glyphStride * (jj + glyphBounds.Top) + 4 * (ii + glyphBounds.Left) + 3]);
if (first || weighted > alpha)
{
alpha = weighted;
first = false;
}
}
}
if (alpha > 0)
{
var q = destStride * (j + s.Bounds.Top) + 4 * (i + s.Bounds.Left);
var pmc = Util.PremultiplyAlpha(Color.FromArgb(alpha, color));
dest[q] = pmc.B;
dest[q + 1] = pmc.G;
dest[q + 2] = pmc.R;
dest[q + 3] = pmc.A;
}
}
}
s.Sheet.CommitBufferedData();
return s;
}
static Color GetContrastColor(Color fgColor, Color bgDark, Color bgLight)
{
return fgColor == Color.White || fgColor.GetBrightness() > 0.33 ? bgDark : bgLight;