Existe-t-il un moyen d'obtenir un effet de type trait sur les bitmaps?

Question

Je voudrais obtenir un bitmap d'effet équivalent à ce que

paint.setStyle(Paint.Style.STROKE) 
canvas.drawText(string, x, y, paint); 

fait pour un texte.

Quelque chose s'apparente à BlurMaskFilter, mais pour un coup, pas de lueur, ni d'ombre.

Ou s'il n'y a pas de manière intégrée, peut-être que quelqu'un peut suggérer un algorithme pour y parvenir?

Answer 1

private Bitmap multiplyAlpha(final Bitmap bitmap, Paint paint, 
     final boolean color, final float x) { 
    paint = new Paint(paint.getFlags()); 
    Bitmap result = Bitmap.createBitmap(bitmap.getWidth(), 
      bitmap.getHeight(), color ? Config.ARGB_8888 : Config.ALPHA_8); 
    // ColorMatrixColorFilter requires ARGB. 
    Bitmap auxiliary = Bitmap.createBitmap(bitmap.getWidth(), 
      bitmap.getHeight(), Config.ARGB_8888); 
    new Canvas(auxiliary).drawBitmap(bitmap, 0, 0, paint); 
    // @formatter:off 
    paint.setColorFilter(new ColorMatrixColorFilter(new float[] { 
       1, 0, 0, 0, 0, 
       0, 1, 0, 0, 0, 
       0, 0, 1, 0, 0, 
       0, 0, 0, x, 0 
    })); 
    // @formatter:on 
    new Canvas(result).drawBitmap(auxiliary, 0, 0, paint); 
    return result; 
} 

private Bitmap opaque(final Bitmap bitmap, Paint paint, final boolean color) { 
    return multiplyAlpha(bitmap, paint, color, 255); 
} 

private RectF inset(final RectF rectF, final float dx, final float dy) { 
    RectF result = new RectF(rectF); 
    result.inset(dx, dy); 
    return result; 
} 

private RectF offset(final RectF rectF, final float dx, final float dy) { 
    RectF result = new RectF(rectF); 
    result.offset(dx, dy); 
    return result; 
} 

private Bitmap antialias(final Bitmap bitmap, Paint paint, 
     final float radius) { 
    Bitmap result = Bitmap.createBitmap(bitmap.getWidth(), 
      bitmap.getHeight(), Config.ALPHA_8); 
    if (radius > 0) { 
     paint = new Paint(paint.getFlags()); 
     Canvas canvas = new Canvas(result); 
     Bitmap opaque = opaque(bitmap, paint, false); 
     canvas.drawBitmap(opaque, 0, 0, paint); 
     paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); 
     paint.setMaskFilter(new BlurMaskFilter(radius, Blur.INNER)); 
     canvas.drawBitmap(opaque, 0, 0, paint); 
    } 
    return result; 
} 

private Bitmap stroke(final Bitmap bitmap, Paint paint, final float radius, 
     final RectF rectF, final float dx, final float dy) { 
    paint = new Paint(paint.getFlags()); 
    Bitmap result = Bitmap.createBitmap(
      (int) Math.ceil(rectF.width() + 2 * radius), 
      (int) Math.ceil(rectF.height() + 2 * radius), Config.ALPHA_8); 
    if (radius > 0) { 
     paint.setMaskFilter(new BlurMaskFilter(radius, Blur.NORMAL)); 
     new Canvas(result).drawBitmap(opaque(bitmap, paint, false), null, 
       offset(rectF, -dx, -dy), paint); 
    } 
    return result; 
} 

private Bitmap stroke(final Bitmap bitmap, Paint paint, final float radius, 
     final RectF rectF, final int color, final float antialias, 
     final float factor, final boolean fill, final float dx, 
     final float dy) { 
    paint = new Paint(paint.getFlags()); 
    Canvas canvas = new Canvas(); 
    paint.setColor(color); 
    Bitmap stroke = stroke(bitmap, paint, radius, rectF, dx, dy); 

    Bitmap auxiliary = Bitmap.createBitmap(stroke.getWidth(), 
      stroke.getHeight(), Config.ALPHA_8); 
    canvas.setBitmap(auxiliary); 
    // Paint [opaque] stroke. 
    canvas.drawBitmap(opaque(stroke, paint, false), 0, 0, paint); 
    // Antialias stroke with outside. 
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); 
    Bitmap outer = multiplyAlpha(antialias(stroke, paint, antialias), 
      paint, false, factor); 

    canvas.drawBitmap(outer, 0, 0, paint); 
    paint.setXfermode(null); 

    // If FILL, leave the inside filled with color (this is the way e.g. 
    // Photoshop strokes); otherwise, the stroke will be only on the outside 
    // of the bitmap; the more transparent the bitmap, the more noticeable 
    // the effect. 
    if (!fill) { 
     paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); 
     canvas.drawBitmap(opaque(bitmap, paint, false), null, 
       offset(rectF, -dx, -dy), paint); 
     paint.setXfermode(null); 
    } 

    Bitmap result = Bitmap.createBitmap(auxiliary.getWidth(), 
      auxiliary.getHeight(), bitmap.getConfig()); 
    canvas.setBitmap(result); 
    RectF output = offset(rectF, -dx, -dy); 
    canvas.drawBitmap(auxiliary, null, inset(output, -radius, -radius), 
      paint); 
    // Paint bitmap. 
    canvas.drawBitmap(bitmap, null, output, paint); 
    // Antialias stroke with bitmap. 
    Bitmap inner = multiplyAlpha(antialias(bitmap, paint, antialias), 
      paint, false, factor); 
    canvas.drawBitmap(inner, null, output, paint); 

    return result; 
} 

private void stroke(final Bitmap bitmap, Paint paint, final float radius, 
     final RectF rectF, final int color, final float antialias, 
     final float factor, final boolean fill, Canvas canvas) { 
    float dx = rectF.left - radius; 
    float dy = rectF.top - radius; 
    Bitmap stroke = stroke(bitmap, paint, radius, rectF, color, antialias, 
      factor, fill, dx, dy); 
    canvas.drawBitmap(stroke, dx, dy, paint); 
} 

où:

• antialias est la largeur de l'anticrénelage effet
• factor modifie la force d'anticrénelage
• fill indique si fauxpeinture que la course à l'extérieur, ou trueal Remplissez donc l'intérieur (ceci est le moyen par ex. Coups de Photoshop); plus transparent le bitmap, plus l'effet est notable
• rectF indique le RectF pour dessiner dans

utilisation

(par exemple):

stroke(bmp, paint, radius, rectF, 0xffff0000, antialias, factor, fill, canvas);