Zxing: generated barcode does not use full width available

Question

I am trying to generate a Code128 barcode using Zxing:

try {
    int width = (int) (barcode.getWidth() * 0.95f);
    int height = (int) (width * 0.2f);
    BitMatrix bitMatrix = writer.encode(code.number, BarcodeFormat.CODE_128, width, height);
    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    for (int i = 0; i < width; i++) {
        for (int j = 0; j < height; j++) {
            bitmap.setPixel(i, j, bitMatrix.get(i, j) ? Color.BLACK : Color.WHITE);
        }
    }
    barcode.setImageBitmap(bitmap);
} catch (WriterException e) {
    e.printStackTrace();
}

Where barcode is an ImageView, whose width is set to match_parent (with 5dp margin) and height is wrap_content. The image I am generating has an aspect ratio of 5:1, and I expected the black stripes to appear in the very beginning of the image, and finish at the very end.

This is what happens, though:

barcode

The ImageView has the green background (note that the image width is 95% of the ImageView width), and the white part belongs to the image. As you can see, there's a huge white area, maybe 40% of the image.

The question is why does the stripes not fill the full (or most of the) width I specified on the writer.encode() method? How can I force this to happen?

Update:

Using different values for the scale type, I noticed that the white margin is present only on the sides of the barcode, and never above or below it.

I tried several scale types, but when I set the green background I realized that the problem is that the image generated by Zxing has that big white margin around the barcode. For the record, the scale type used on the picture above is `CENTER_INSIDE` — Guilherme, Jul 21 '14 at 13:33

score 7 · Answer 1 · answered Jul 21 '14 at 14:12

7

The bars in the barcode have to have widths that are an integer number of pixels, or else you'd get some distortions. The barcode is as wide as it can be satisfying these constraints.

A good solution for this use case is to set the width to 1. This will force the image to be as small as possible; narrow bars will be one pixel. Then you can let Android scale it exactly as you like.

answered Jul 21 '14 at 14:12

Sean Owen

66,182
23
141
173

I tried to set both width and height to 1, but now the whole image is a white square. – Guilherme Jul 21 '14 at 14:23
1

This worked great for me. @Guilherme don't set the height to 1, just the width. – Matt Mills Oct 24 '14 at 21:41

score 2 · Accepted Answer · answered Jul 21 '14 at 20:23

This is not the most generic answer, but that's how I solved it:

My code uses Code128 standard, where each symbol is a combination of 11 stripes (either black or white. The code also has a fixed length, 20 characters. So I forced the writer to encode using a width of 20 * 11 pixels. That did work, the the quiet zone around the code was minimal.

For the scaling purpose, however, that width was not good enough. Depending on the screen, the image would not be scaled in a good way, distorting the stripes in a non-even way, making the code unreadable. Then I choose to oversample the image, using this time 20 * 11 * 4 pixels. The results were much better, because now the image is being scaled down, and not up as before.

The oversample factor may vary depending on the dimension you need to display, but if you're in a similar situation, with fixed length of the barcode and each symbol, this is an easy way to get a nice barcode with minimal quiet zone and does not involve any further image processing.

This one worked for me. For me I had a length of 16 characters so I multiplied by `11 * 4` and put this on the width for my html image width. — Sha, Jul 27 '21 at 13:09

score 0 · Answer 3 · answered Dec 15 '15 at 07:35

0

I solved that problem by adding

android:layout_marginRight="-30dp"
android:layout_marginLeft="-30dp"

to ImageView with barcode.

answered Dec 15 '15 at 07:35

Krzysztof Dziuba

581
6
9

Zxing: generated barcode does not use full width available

3 Answers3