带有字体的 Android Canvas 旋转文本未正确保存在 SD 卡上

Question

我在 Canvas 上绘制旋转文本，然后将其以 JPEG 格式保存到 SD 卡。我面临的问题是 Canvas 预览看起来不错，但保存图像中的旋转文本显示不正确。当我使用默认的 Android 字体时，最终的 JPEG 与 Canvas 预览相同，但此代码不适用于自定义字体。

I have uploaded both the final saved image and screenshot of canvas preview

我正在为 Canvas 绘图使用自定义 View 类，这是我的代码

public class MyBringBack extends View {


    Bitmap bitmap;
    Typeface type;

public MyBringBack(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        type = Typeface.createFromAsset(context.getAssets(),"fonts/rockwell-bold.ttf"); 
         setDrawingCacheEnabled(true);
    }


@Override
protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);



    Paint paint = new Paint();
        paint.setColor(Color.BLUE);
       // paint.setTypeface(Typeface.defaultFromStyle(Typeface.BOLD));
        paint.setTextSize(23);
    Paint paint1 = new Paint();
        paint1.setTextSize(40);
        paint1.setColor(Color.RED);

        canvas.rotate(90,434,110);
        canvas.drawText("Demo Text Demo Text Demo Text  ", 434, 110, paint);
        canvas.restore();
        canvas.save();
        paint1.setTypeface(type);
        canvas.rotate(90,130,185);
        canvas.drawText("Text using Typeface ", 130, 185, paint1);
        canvas.restore();
        canvas.save();
        canvas.rotate(90,180,185);
        canvas.drawText("Text using Typeface ",180, 185, paint1);
        canvas.restore();
        canvas.save();
        canvas.rotate(90,230,185);
        canvas.drawText("Text using Typeface ", 230, 185, paint1);
        canvas.restore();
        canvas.save();

        this.setDrawingCacheEnabled(true);
        Bitmap c= Bitmap.createScaledBitmap(this.getDrawingCache(), canvas.getWidth(),canvas.getHeight(), false);

        /* Saving File To SD Card   */

        OutputStream outStream = null;
        File bgv = new File("/sdcard/");
        /* To build directory if needed */
        bgv.mkdirs();

        File file = new File(bgv, "final22.jpg");

        try {
        outStream = new FileOutputStream(file);
        c.compress(Bitmap.CompressFormat.JPEG, 100, outStream);

        outStream.flush();
        outStream.close();

      } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();

       } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
       }

    }

我的代码有问题吗？

请帮忙...

提前致谢:)

Answer 1

经过对图像处理的大量研究，我终于得到了答案。为了保存与在 Canvas 上绘制的完全相同的 jpg，我们只需添加两行代码。首先是:

setDrawingCacheQuality(DRAWING_CACHE_QUALITY_HIGH);

然后在onDraw中我们必须将AntiAlias设置为true，引用我的代码

paint1.setAntiAlias(true);

但在此之后，保存的图像与在 Canvas 上绘制的图像质量也不一样。要获得同样清晰的图像质量，这两个代码可以解决问题

paint1.setDither(true);
paint1.setFilterBitmap(true);

Dither 主要提供光滑的边角，AntiAlias、Dither 和 FilterBitmap 也可以在 Canvas 上绘制 Bitmap 时使用。

要获得更多关于 Dither 和 AntiAlias 的信息，请点击此处

AntiAlias

Dither