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Why does BitmapFactory.decodeByteArray return null?

Tags:

java

android

It's the simple code and instead of getting result to set the Bitmap, I get null. Can anyone tell me where I am making a mistake?

String test = "test";
byte[] byteA = test.getBytes();
Bitmap bmp = BitmapFactory.decodeByteArray(byteA, 0, byteA.length); //<- I get null here
ImageView image = (ImageView) findViewById(R.id.image);
image.setImageBitmap(bmp);

UPDATE

Ok, so I cannot convert text to image like I thought I could. How about this way? Will this create a bitmap?

  Paint paint = new Paint();
    paint.setStyle(Paint.Style.FILL);
    paint.setColor(Color.RED);
    paint.setTextSize(16);
    paint.setAntiAlias(true);
    paint.setTypeface(Typeface.MONOSPACE);

    Bitmap bm = Bitmap.createBitmap(16, 16, Bitmap.Config.ALPHA_8);
    float x = bm.getWidth();
    float y = bm.getHeight();
    Canvas c = new Canvas(bm);
    c.drawText("Test", x, y, paint);
like image 597
sandalone Avatar asked Jun 29 '11 12:06

sandalone


2 Answers

In such case you need to convert the string to Base64 first.

String strImage = geTImageAsHexString();
byte[] x = Base64.decode(strImage, Base64.DEFAULT);  //convert from base64 to byte array
Bitmap bmp = BitmapFactory.decodeByteArray(x,0,x.length);
like image 81
Mustafa Güven Avatar answered Sep 18 '22 14:09

Mustafa Güven


From the documentation:

Returns The decoded bitmap, or null if the image could not be decode.

The bytes involved in the string "test" aren't a valid bitmap, are they?

If you saved the text "test" in a file called foo.png or foo.jpg etc and tried to open it in Windows, what would you expect the result to be? It would be an error: those bytes simply aren't a valid image in any known format.

EDIT: I don't know anything about Android graphics, but your update certainly looks like a much more reasonable way to draw text onto a bitmap.

like image 28
Jon Skeet Avatar answered Sep 20 '22 14:09

Jon Skeet