how to extract image from pdf using mupdf? - visual-c++

Question

I want to extract image from pdf and save the image handle to std::vector,some time the background is incorrect,my code is follow.
BOOL CTextEditorDoc::loadImage()
{
if(m_strPDFPath.IsEmpty())
return FALSE;
CString strFile;
fz_context *ctx;
fz_document* doc;
fz_device *dev;
fz_irect bbox;
fz_rect bounds;
fz_matrix ctm;
fz_pixmap *image;
fz_colorspace *colorspace;
int i,j,rotation = 0;
int pagecount = 0;
fz_page *page;
BITMAPINFO bmi;
HBITMAP hBitmap;
LPBYTE pDest,pImage;
if(!gb2312toutf8(m_strPDFPath,strFile))
return FALSE;
ctx = fz_new_context(NULL, NULL, FZ_STORE_UNLIMITED);
fz_try(ctx){
doc = fz_open_document(ctx,strFile.GetBuffer(0));
}fz_catch(ctx){
fz_free_context(ctx);
return FALSE;
}
fz_rotate(&ctm, rotation);
colorspace = fz_device_rgb(ctx);
pagecount = fz_count_pages(doc);
pDest = NULL;
::ZeroMemory(&bmi, sizeof(BITMAPINFO));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biWidth = 180;
bmi.bmiHeader.biHeight = -180;
bmi.bmiHeader.biSizeImage = 180*180*4;
for(i=0;i<pagecount;i++){
page = fz_load_page(doc,i);
if(i == 0){
fz_bound_page(doc,page,&bounds);
fz_pre_scale(&ctm,180/(bounds.x1 - bounds.x0),180/(bounds.y1 - bounds.y0));
fz_transform_rect(&bounds, &ctm);
fz_round_rect(&bbox, &bounds);
}
image = fz_new_pixmap_with_bbox(ctx,colorspace,&bbox);
dev = fz_new_draw_device(ctx,image);
fz_try(ctx){
fz_run_page(doc,page,dev,&ctm,NULL);
}fz_catch(ctx){
fz_drop_pixmap(ctx,image);
fz_free_device(dev);
fz_free_page(doc, page);
continue;
}
pImage = image->samples;
if(pImage){
pDest = NULL;
hBitmap = ::CreateDIBSection(NULL,&bmi,DIB_RGB_COLORS,(void**)&pDest,NULL,0);
ASSERT(hBitmap);
if(image->n == 2){ //not pallet
for (j = 180* 180; j > 0 ; j--){
pDest[0] = pDest[1] = pDest[2] = *pImage++;
pDest[3] = *pImage++;
pDest += 4;
}
}else if(image->n == 4){
//memcpy(pDest,pImage,m_thumbWidth * m_thumbHeight*4);
for (j = 180* 180; j > 0 ; j--){
pDest[0] = *pImage++;
pDest[1] = *pImage++;
pDest[2] = *pImage++;
pDest[3] = *pImage++;
pDest += 4;
}
}else ASSERT(FALSE);
m_imageVector.push_back(hBitmap);// save it to std::vector
}
fz_drop_pixmap(ctx,image);
fz_free_device(dev);
fz_free_page(doc, page);
}
fz_close_document(doc);
fz_free_context(ctx);
return TRUE;
}
this code can extract all the image of pdf but it maybe too slow ,how to improve it ?
some time the image's background is incorrect?
left of the follow picture is incorrect,right of the follow picture is real.

Answer 1

Like in the example of http://mupdf.com/docs/example.c
you forgot
fz_clear_pixmap_with_value(ctx, pix, 0xff);
to white the pixmap