Barcode drawing question

[Ezio]

Hi Loic,
I need create a Bitmap with 1D barcode on it.

Follwing a code excerpt i write.

Code: Select all

Calling code excerpt

        private string Encoded_Value = "";
        private Barcode1DWriterType Encoded_Type = Barcode1DWriterType.Barcode1DWriterCode39;
        private Image _Encoded_Image = null;
        private Color _ForeColor = Color.Black;
        private Color _BackColor = Color.White;
        private int _Width = 400;
        private int _Height = 100;
        private bool _IncludeLabel = false;
        private Font _LabelFont = new Font("Microsoft Sans Serif", 10, System.Drawing.FontStyle.Bold);
        private BarcodeAlign _Alignment = BarcodeAlign.BarcodeAlignCenter;
        private LabelPositions _LabelPosition = LabelPositions.BOTTOMCENTER;
        private RotateFlipType _RotateFlipType = RotateFlipType.RotateNoneFlipNone;
        private GdPictureImaging GDImaging = new GdPictureImaging();
        private string LicenseNumber = "XXXX"; 
        private string LicenseNumberUpgrade = "YYYY";
        private string gdError;

                       .
                       .
                       .
                       .

            Encoded_Value = "0800853012780";   //"BCODE";
            Encoded_Type = Barcode1DWriterType.Barcode1DWriterCode39;
            IncludeLabel =  true;
            Alignment = BarcodeAlign.BarcodeAlignCenter;
            LabelPosition = LabelPositions.BOTTOMCENTER;
            RotateFlipType = RotateFlipType.RotateNoneFlipNone;
                topOffset = leftOffset = 0;

            //===== Encoding performed here =====
            bcw = 2 * leftOffset;
            bch = topOffset;
            if (IncludeLabel == true)
                bch += topOffset;

            if (BarcodeDraw(Encoded_Type, EncodeData, IncludeLabel, leftOffset, topOffset, Width - bcw, Height - bch, Color.Black, Alignment, (float)RotateFlipType) == false)
                MessageBox.Show(gdError);



// function to draw barcode e return a Bitmap
 private bool BarcodeDraw(Barcode1DWriterType bcType, string bcData,bool drawLabel, int left, int top, int width, int height, Color barColor,BarcodeAlign Alignment, float angle)
        {
            GdPictureStatus GdRet;

             GDImaging.SetLicenseNumberUpgrade(LicenseNumber, LicenseNumberUpgrade);

            int pImageID = GDImaging.CreateNewGdPictureImage(Width, Height, 24, BackColor);
            
            GdRet = GDImaging.Barcode1DWrite(pImageID, bcType, bcData, left, top, width, height,barColor, Alignment, angle);
            gdError = GdRet.ToString();

            if (GdRet != GdPictureStatus.OK)
                return false;
            
            Bitmap = GDImaging.GetBitmapFromGdPictureImage(pImageID);

            if (drawLabel == true)
                Add_Label(Bitmap);     // Add code string

            GDImaging.ReleaseGdPictureImage(pImageID);
            // rilascia le risorse allocate da GDPicture
            GDImaging.ClearGdPicture();
            return true;
        }

When I call the function BarcodeDraw() with this parameters:
width = 400, height = 100, top = 0, left = 0
I get expected image (see 400x100.bmp)

If I reduce width to 350 I get a small barcode centered in image (see 350x100.bmp)

Please can you explain logic used to calc width of bars??
Thank you in advance.

[Ezio]

Images.zip

barcodes image file

(4.23 KiB) Downloaded 402 times

Ooops attchments

[Loïc]

Hi Ezio,

Could you provide a code snippet that i can run as is ?

Thank you for your understanding.

Kind regards,

Loïc

[Ezio]

prova.zip

Test project

(35.14 KiB) Downloaded 420 times

Hi Loic,
in attached file you can find a sample code I use to create barcode.

I tried from 250x100 to 400x100 barcode size and it seems to change bars dimension starting at 390x100.
creating different barcode size, I get same barcode from 250 to 380 pixel width.

Kind Regards
Ezio

[Loïc]

Ezio, thank you very much for the clear application.

I understand the issue now. Let me explain:

Based on the width parameter passed to the barcode drawing engine, a minimum bar width will be computed. This bar width must be a real value > 0. IE: 1, 2, 3, 4...

In situation 1, the min bar width is equal to 1.
In situation 2, the min bar width is equal to 2.

Therefore, in the situation 2 the engine will be able to use more space to render the barcode than in situation 1. This explains why the produced barcode is wider.

If you want to get the same barcode width in any situation you have to:
- Determines the minimum width needed to paint a barcode with a bar width of 1. See method: Barcode1DWriteGetMinWidth()
- Create a tmp bitmap of the computed width. For the height I suggest width /3, but you can use any value.
- And then, render the tmp bitmap on your bitmap in which you want to see your barcode.

But keep in mind: this method implies to interpolate your barcode bars which usually results in a harder barcode detection (if any).

I hope my explanations are clear enough. Let me know there is something you do not understand.

Kind regards,

Loïc

[Ezio]

Loic, thank you for your explanation. This is what I imagined.
I need produce surely readable barcode at low resolution, usually images are scanned at 200DPI resolution.

To get this result I must create barcode where thin bar is always 3 pixel at least when is scanned at 200 DPI, or if you prefer about 4/10 mm.

if I understand I must proceed as follow:
1 - I get minimum width required to draw a barcode with thin bar dimension of 1 Pixel, using method: Barcode1DWriteGetMinWidth()
2 - I create a GdPictureImage where the width will be calculated as the result of previous call multiply by 3, at least.
3 - I create barcode on it and the thin bar will be about 4/10 mm.

Is this a correct approach to provide a solution to my problem?
can you comfirm this or I misunderstood your explanations?

Kind regards
Ezio