From: johne AT parallax DOT co DOT uk (John Eccleston)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Help with this PCX displaying source (in DJGPP & GRX)
Date: Fri, 07 Feb 97 09:15:59 GMT
Organization: Parallax Solutions Ltd
Message-ID: <855306894.195021@red.parallax.co.uk>
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 "Gautam N. Lad" wrote:
>Hi,
>Can someome please help me with this PCX displaying source.  It
>works for one image, a friend sent, but others don't work.  WHY?
>It seems right to me.
>
>I've been looking for a PCX displaying source in DJGPP & GRX
>and now that I have it, it doesn't work.
>
>NOTE:  I won't be using 320x200 images only.  I might be using a 
>       smaller size.
>

Hi Gautam,

Something I found with PCX files is that the rows are always padded to 
even byte boundaries, so for example if an image has a width of 27 and
a height of 30 pixels then the compressed data is padded to lines of 28
pixels.

In the header of the PCX is a field which tells you how many bytes per
line are used to store the image.  Use this to read the bytes and just
ignore those that are over the image width here is my structure that
defines the header of a PCX file.  Load this first to get the information
about the file.

-----> Cut here <-----
typedef struct PCXHeader
{
   BYTE manufacturer PACKED; /* Manufacturers code always 0 */
   BYTE version      PACKED; /* Always 5 for 256 colour images */
   BYTE encoding     PACKED; /* Always set to 1 for RLE */
   BYTE bitsPerPixel PACKED; /* Should be 8 for 256 colour files */
   WORD minX         PACKED; /* Minimum Y screen coord */
   WORD minY         PACKED; /* Minimum X screen coord */
   WORD maxX         PACKED; /* Maximum X screen coord */
   WORD maxY         PACKED; /* Maximum Y screen coord */
   WORD horizRes     PACKED; /* Horizontal resolution of the image */
   WORD vertRes      PACKED; /* Vertical resolution of the image */
   BYTE palette[48]  PACKED; /* EGA palette, not used for 256 colour files */

   BYTE reserved     PACKED; /* Reserved for future use */

   BYTE colourPlanes PACKED; /* Number of colour planes */
   WORD bytesPerLine PACKED; /* Number of bytes per line of the image */
   WORD paletteType  PACKED; /* Should be 2 for colour palette */
   
   BYTE filler[58]   PACKED; /* Reserved for future use */
} PCXHeader;
-----> Cut here <-----

If you would like the whole of my PCX loading code then please email me.

Hope this helps

John

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