Paint绘制一张图片

1.使用画笔绘制一张Bitmap

Canvas canvas = null;
        Bitmap bitmap = null;
        try {
            TextPaint textPaint = new TextPaint();
            textPaint.setColor(Color.argb(255, 0, 0, 255));
            textPaint.setTypeface(Typeface.SANS_SERIF);
            textPaint.setTextSize(60);

            Paint bgPaint = new Paint();
            bgPaint.setStyle(Paint.Style.FILL);
            bgPaint.setARGB(127, 0, 0, 0);

            int bmpWidth = (int) textPaint.measureText(content);
            if (bmpWidth % 4 != 0) {
                bmpWidth = bmpWidth - bmpWidth % 4 + 4;
            }

            Paint.FontMetrics fm = textPaint.getFontMetrics();
            int bmpHeight = (int) Math.ceil(fm.bottom - fm.top);
            if (bmpHeight % 4 != 0) {
                bmpHeight = bmpHeight - bmpHeight % 4 + 4;
            }

            bitmap = Bitmap.createBitmap(bmpWidth, bmpHeight, Bitmap.Config.ARGB_8888);
            canvas = new Canvas(bitmap);
            canvas.drawRect(0, 0, bmpWidth, bmpHeight, bgPaint);
            canvas.drawText(content, 0, Math.abs(fm.top), textPaint);
        } catch (StringIndexOutOfBoundsException e) {
            return false;
        } catch (Exception e) {
            return false;
        }

FontMetrics源码

/**
     * Class that describes the various metrics for a font at a given text size.
     * Remember, Y values increase going down, so those values will be positive,
     * and values that measure distances going up will be negative. This class
     * is returned by getFontMetrics().
     */
    public static class FontMetrics {
        /**
         * The maximum distance above the baseline for the tallest glyph in
         * the font at a given text size.
         */
        public float   top;
        /**
         * The recommended distance above the baseline for singled spaced text.
         */
        public float   ascent;
        /**
         * The recommended distance below the baseline for singled spaced text.
         */
        public float   descent;
        /**
         * The maximum distance below the baseline for the lowest glyph in
         * the font at a given text size.
         */
        public float   bottom;
        /**
         * The recommended additional space to add between lines of text.
         */
        public float   leading;
    }

FontMetrics使用说明请参考：https://blog.csdn.net/u012551350/article/details/51361778

ascent = ascent线的y坐标 - baseline线的y坐标；//负数

descent = descent线的y坐标 - baseline线的y坐标；//正数

top = top线的y坐标 - baseline线的y坐标；//负数

bottom = bottom线的y坐标 - baseline线的y坐标；//正数

leading = top线的y坐标 - ascent线的y坐标；//负数