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feat(core): render local CJK glyphs at 2x texture resolution (#4304)

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Bart Louwers <bart@emeel.net>
This commit is contained in:
Taku Fukada
2026-07-01 20:52:01 +09:00
committed by GitHub
parent 60f15190c3
commit 887e6021e6
22 changed files with 357 additions and 84 deletions
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60
platform/android/MapLibreAndroid/src/main/java/org/maplibre/android/text/LocalGlyphRasterizer.java
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@@ -4,38 +4,76 @@ import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Typeface;
import androidx.annotation.Keep;
import androidx.annotation.NonNull;
import androidx.annotation.WorkerThread;
import java.util.HashMap;
import java.util.Map;
/**
* LocalGlyphRasterizer is the Android-specific platform implementation used
* by the portable local_glyph_rasterizer.hpp
*/
@Keep
public class LocalGlyphRasterizer {
private static final int TEXTURE_SCALE = 2;
private static final int BITMAP_SIZE = 60;
private static final int TEXT_SIZE = 48;
private static final int RASTER_BUFFER = 3 * TEXTURE_SCALE;
private static final float TOP_ADJUSTMENT = 26.5f;
private static final float BASELINE_X = 10;
private final Bitmap bitmap;
@NonNull
private final Paint paint;
@NonNull
private final Canvas canvas;
@NonNull
private final Rect textBounds;
@NonNull
// Tiny cache (font stacks × 2 for bold/regular) so glyphs don't
// pay Typeface.create's cache lookup and internal lock per call.
private final Map<String, Typeface> typefaceCache;
// Updated by drawGlyphBitmap so native code can read the measured top without
// allocating a per-glyph result object.
private float glyphTop;
LocalGlyphRasterizer() {
/*
35x35px dimensions are hardwired to match local_glyph_rasterizer.cpp
These dimensions are large enough to draw a 24 point character in the middle
of the bitmap (y: 20) with some buffer around the edge
60x60px dimensions are hardwired to match local_glyph_rasterizer.cpp.
Glyphs are drawn at 2x texture resolution, while logical metrics stay at 1x.
These dimensions are large enough to draw a 48 px character in the middle
of the bitmap with some buffer around the edge.
*/
bitmap = Bitmap.createBitmap(35, 35, Bitmap.Config.ARGB_8888);
bitmap = Bitmap.createBitmap(BITMAP_SIZE, BITMAP_SIZE, Bitmap.Config.ARGB_8888);
paint = new Paint();
paint.setAntiAlias(true);
paint.setTextSize(24);
paint.setTextSize(TEXT_SIZE);
canvas = new Canvas();
canvas.setBitmap(bitmap);
textBounds = new Rect();
typefaceCache = new HashMap<>();
}
private void setTypeface(String fontFamily, boolean bold) {
String key = (bold ? "bold:" : "regular:") + fontFamily;
Typeface typeface = typefaceCache.get(key);
if (typeface == null) {
typeface = Typeface.create(fontFamily, bold ? Typeface.BOLD : Typeface.NORMAL);
typefaceCache.put(key, typeface);
}
paint.setTypeface(typeface);
}
private int measureGlyphTop(String glyph) {
paint.getTextBounds(glyph, 0, glyph.length(), textBounds);
return Math.max(0, -textBounds.top);
}
/***
@@ -51,9 +89,17 @@ public class LocalGlyphRasterizer {
*/
@WorkerThread
protected Bitmap drawGlyphBitmap(String fontFamily, boolean bold, char glyphID) {
paint.setTypeface(Typeface.create(fontFamily, bold ? Typeface.BOLD : Typeface.NORMAL));
setTypeface(fontFamily, bold);
String glyph = String.valueOf(glyphID);
int glyphTopPx = measureGlyphTop(glyph);
glyphTop = glyphTopPx / (float) TEXTURE_SCALE - TOP_ADJUSTMENT;
canvas.drawColor(Color.WHITE);
canvas.drawText(String.valueOf(glyphID), 5, 25, paint);
canvas.drawText(glyph, BASELINE_X, RASTER_BUFFER + glyphTopPx, paint);
return bitmap;
}
@WorkerThread
protected float getLastGlyphTop() {
return glyphTop;
}
}