why FPDFImageObj_GetBitmap return null?

[薛龙]

why FPDFImageObj_GetBitmap return null?

it is FPDF_PAGEOBJ_IMAGE,when i use FPDFPageObj_GetType.

i can use funciton bellow to get data,

int newSize = FPDFImageObj_GetImageDataRaw(pdfObj, pByte, size).

 i debug the code , i find 

RetainPtr<CPDF_Image> pImg = pImgObj->GetImage();

pImg  is not null, 

const CPDF_Stream* pImgStream = pImg->GetStream();

the pImgStream is not bull. 

also  i can see the height and width.

 i think it is a real exised picture inside, but  how can i get it , and  what 

this picture is ?