Solution : https://service.sap.com/sap/support/notes/204770 (SAP Service marketplace login required)
Key words : 
create bw web report graphics, bw web report, additional key words, char ocx instantiation, symptom graphics, web reporting, prerequisites calling, program directory, purpose register, files chart
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| 445644 | BW Web Report Charts on Windows CE | 
| 432458 | Display of blank cells in BW report charts | 
| 424099 | Analysis of BW 2.0B/2.1C Web Reporting problems | 
| 422582 | |
| 331778 | Correction for the ITS 4.6D for BW 2.0B | 
| 331775 | Correction of the ITS 4.6C for BW 2.0B | 
| 209420 | Charts are not displayed in BW web reporting | 
| 207452 |