【转帖】reading embedded rasters
 

reading embedded rasters
reading embedded rasters
i am importing hybrid dwf files (contain raster and vector entities) and then trying to read the raster data from them. when i look in the debugger i can see that the oddbrasterimage contains an embeddedraster which contains the extension, name and data for the image. however, i cannot figure out how to access the data.
when i access the odgirasterimage i can get the pixelwidth and pixelheight just fine, but colordepth is zero. what is worse is that when i use scanline to access the data an exception is thrown.
how does one read an embeddedraster?
here is the code i am using that does not work (eliminating the stuff not dealing with reading the file):
code:
int readembeddedimage(odgirasterimageptr praster)
{
long raswidth = praster->pixelwidth(); // works
long rasheight = praster->pixelheight(); // works
long bitsperpixel = praster->colordepth(); // returns zero
if (bitsperpixel == 0)
bitsperpixel = 24;
long scanlinesize = praster->scanlinesize(); // returns zero
unsigned char *psclns = new unsigned char[raswidth*3];
for (long ln = 0; ln < rasheight; ln++)
{
praster->scanlines(psclns, ln); // dies here
unsigned char *pscan = psclns;
for (long wd=0; wd < raswidth; wd++)
{
clr.blue = *pscan++;
clr.green = *pscan++;
clr.red = *pscan++;
if ((clr.blue != 255) || (clr.green != 255) || (clr.red != 255))
cout << clr.blue << "/" << clr.green << "/" << clr.red << endl;
}
}
embeddedimagedef is declared in
imports\dwfimport\source\embeddedimagedef.h
you may use it directly, to access image data stream. this is a dirty hack of course.
to use scanlines() etc. you have to implement a raster service that will load the raster from stream and convert it to a bitmap. (look at extensions\exservices\exgirasterimage.cpp exrastermodule::loadrasterimage())
vladimir