Crystal report dynamic image change quality problem

Hi, 

i am using crystal report and dotnet charting 2005 tools if  report  generating time combine the two tools and exporting pdf file.my problem is exporting time combine both exporting working fine,but chart image quality is very low.

the following method i use: 

I Create a dataset which one of the field in the data table is base64binary.
After retrieval of the file path, open the file and store the image file as array of byte in that column.
When you bind the dataset to your report as the data source, you can easily drag and drop the image field to your report.

Conversion of image file to array of byte:
Dim fs As New System.IO.FileStream(<file path>, IO.FileMode.Open)
Dim br As New System.IO.BinaryReader(fs)
Dim arrayByte() As Byte
arrayByte = br.ReadBytes(CInt(fs.Length))
br.Close()
fs.Close()

how i to solve t his problem. any one give any idea?

Regards

Vadivel.A