Jump to content
  • Advertisement
Sign in to follow this  
mattxander12

Unpacking an int

This topic is 3980 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I'm doing a school project currently that does actions on a bmp such as widening a bitmap , mirroring it etc. When I widen a BMP, I have to change the value of the width in pixels and file length in the BMP header. I must do this all in C and cannot use any pre-defined structures that would make it easier. The machine I have to compile on is a Sparc machine and it is Big Endian. Here's how I pack the length of the bmp file...
short sResult;
int iResult;
int fileSize;
int i;

for(i = 0; i < 4; i++)
{
  sResult = bmpFile[5-i];
  iResult = iResult << 8;
  iResult = iResult | sResult; 
}
fileSize = iResult;
But I have no idea how to go about extracting bits from this variable to write back into the bmp Header file once I calculate new values for the file length and bmp width. Could someone give me a nudge in the right direction ? Thanks! --Matt

Share this post


Link to post
Share on other sites
Advertisement
>> shifts in the opposite direction as <<, allowing you to return things to the low-order bits.

bitwise-and (&) can be used to mask off high-order bits.

Assuming you actually understand what your existing code does, you should be quite well nudged enough now :)

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!