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[Code]Loading a PCX file

 
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Ferrero



Joined: 19 Dec 2005
Posts: 15
PostPosted: Fri Jan 06, 2006 2:03 am    Post subject: [Code]Loading a PCX file Reply with quote
Hi everybody, I've developped a little class to load and blit a PCX file.

The interest of this :

- You can have an image larger than 512x512 pixels.

Another thing :

- As a PCX file is an indexed color image file (compressed), finally you have an array of byte which you can fill with a picture editor. So in this file you can store a map to have a 2D tiled game, and this file is compressed.

Here's the class :
Code:

-------------------------------------------------------------------------------         
--
--   Author      :   Lepecq Michael (Ferrero)
--   Version      :   1.0
--   Copyright   :   2005 - 2006      
--
-------------------------------------------------------------------------------
--
--  This object is designed to manage PCX Files
--
--  Methods :
--
--      Public :
--         
--         load : load a PCX file
--
--      Private :
--
--         decodeHeader    : Decode the header of a pcx file
--         loadPalette256   : Load the 256 colors palette of the file
--         readPixel      : Read the Pixel of the file
--
--   Properties :
--   
--
--      Public :
--
--         BitsPerPixel       : The number of bits per pixel per plane in the image data.
--         MaxNumberOfColors    : The maximum number of colors allowed in the file
--         Palette            : Hold the different colors of the image
--         ImageWidth         : Width of the image in pixel
--         ImageHeight         : Hieght of the image in scanlines
--         BlitTo            : Blit the PCX to an image
--
--      Private :
--
--         XStart          : Left of the image
--         YStart          : Top of the image
--         XEnd          : Right of the image
--         YEnd          : Bottom of the image
--         NumBitPlanes   : Number of bit planes
--         BytesPerLine   : Length of an unencoded line in a plane
--         ScanLineLength   : Length of an unencoded line
--         Pixel         : Array of pixels [y][x]
--         LinePaddingSize : Padding of a scanline (end of a scan line)
--
-------------------------------------------------------------------------------

clsPCX =
{
    BitsPerPixel = 0,
    XStart       = 0,
    YStart       = 0,
    XEnd       = 0,
    YEnd       = 0,
    NumBitPlanes = 0,
    MaxNumberOfColors = 0,
    BytesPerLine = 0,
    Palette       = {},
    ImageWidth    = 0,
    ImageHeight  = 0,
    Pixel       = {},
    LinePaddingSize = 0
}

function clsPCX:new()
   mtbPCX = {};
   setmetatable(mtbPCX, self);
   self.__index = self;
   return mtbPCX;
end

function clsPCX:load(filename)
   
   local file     = assert(io.open(filename, "rb"));
    local header = file:read(128);
   
    -- Decoding the header
   
    assert(self:decodeHeader(header));
     
   -- Reading the Pixel
   
   assert(self:readPixel(file));
   
    -- Loading the palette
   
    if (self.MaxNumberOfColors == 256) then
       assert(self:loadPalette256(file));
   else   
      return nil, "This palette mode is not supported yet";
   end
   
   -- Closing the file
   
    assert(file:close());
   
    return true
   
end

function clsPCX:decodeHeader(header)
   
   if (string.byte(header, 1) == 10) then
      
      self.BitsPerPixel = string.byte(header, 4);
      self.XStart   = string.byte(header, 6) * 256 + string.byte(header, 5);
      self.YStart   = string.byte(header, 8) * 256 + string.byte(header, 7);
      self.XEnd   = string.byte(header, 10) * 256 + string.byte(header, 9);
      self.YEnd   = string.byte(header, 12) * 256 + string.byte(header, 11);
      self.NumBitPlanes = string.byte(header, 66);
      self.BytesPerLine = string.byte(header, 68) * 256 + string.byte(header, 67);
      
      self.MaxNumberOfColors = (2^self.BitsPerPixel * self.NumBitPlanes);
      self.ScanLineLength = self.NumBitPlanes * self.BytesPerLine;
      self.ImageWidth  = self.XEnd - self.XStart + 1;
      self.ImageHeight = self.YEnd - self.YStart + 1;
      self.LinePaddingSize = ((self.BytesPerLine * self.NumBitPlanes) * (8 / self.BitsPerPixel)) - ((self.XEnd - self.XStart) + 1);
   
   else
      return nil, "This is not a valid PCX file";
   end
   
   return true;
end

function clsPCX:loadPalette256(file)

    file:seek("end", -769);
    local CheckByte = file:read(1);
    local Palette   = file:read(768);
   local j=0;
   local i=0;   
   
    if (string.byte(CheckByte) == 12) then
       for i=1,768,3 do
          self.Palette[j] = Color.new(string.byte(Palette, i), string.byte(Palette, i+1), string.byte(Palette, i + 2));
          j = j + 1;
          
       end
   else
      return nil, "256 colors palette not found:"..CheckByte;
   end
   
    return true;
   
end

function clsPCX:readPixel(file)

   local y;
   local runcount;
   local byte;
   local x;
   local i;

   for y=0,self.ImageHeight-1 do
      self.Pixel[y] = {};
      x = 0;
      while (x<self.ScanLineLength) do
         
         byte = string.byte(file:read(1));
         if (byte >= 192) then
            runcount = byte - 192;
            byte = string.byte(file:read(1));
            for i=0, runcount do
               self.Pixel[y][x+i] = byte;
            end
            x = x + runcount;
            
         else
            
            self.Pixel[y][x] = byte;
            x = x + 1;
         end
         
      end
      
   end
   
    return true;
   
end

function clsPCX:blitTo(image_x, image_y, image, rect_left, rect_top, rect_right, rect_bottom)

   local line;
   local y;
   local x;
   local color;
   
   local ymin;
   local ymax;
   local xmin;
   local xmax;
   
   -- Computing the clipping
   
   if image_y < 0 then
      rect_top = rect_top - image_y;
      ymin = 0;
   else
      ymin = image_y;
   end
   
   if image_x < 0 then
      rect_left = rect_left - image_x;
      xmin = 0;
   else
      xmin = image_x;
   end
   
   if ymin + (rect_bottom - rect_top) >= image:height() then
      ymax = image:height() - 1;
   else
      ymax = ymin + (rect_bottom - rect_top);
   end
      
   if xmin + (rect_right - rect_left) >= image:width() then
      xmax = image:width() - 1;
   else
      xmax = xmin + (rect_right - rect_left);
   end
   
   if (xmax + rect_left >= self.ImageWidth) then
      xmax = self.ImageWidth - rect_left - 1;
   end
   
   if (ymax + rect_top >= self.ImageHeight) then
      ymax = self.ImageHeight - rect_top - 1;
   end
   
   -- Drawing the image
   
   for y=ymin,ymax do
      
      line = rect_top + y - image_y;
      
      for x=xmin, xmax do
         color = self.Palette[self.Pixel[line][rect_left + x - image_x]];
         image:pixel(x, y, color);
      end   
      
   end

    return true;
   
end


And how to use it :

Code:

map=clsPCX:new();
assert(map:load("..\\maps\\map1560.pcx"));

screen:clear();
map:blitTo(0,0,screen,0,0,480,272);
screen.flip();
control = Controls.read();

while control:start() == false do   
   control = Controls.read();
   screen.waitVblankStart();
end
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LuMo



Joined: 21 Aug 2005
Posts: 410
Location: Austria
PostPosted: Fri Jan 06, 2006 3:43 am    Post subject: Reply with quote
how fast is it?
did you test it running compared to normal blit?
greets
lumo

PS: interesting!
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Ferrero



Joined: 19 Dec 2005
Posts: 15
PostPosted: Fri Jan 06, 2006 6:17 pm    Post subject: Reply with quote
The blit is quite slow,

I use it like this :

First, I blit it to an 512*512 image and I use this image to blit onto the screen.
And when the image does not contain the needed datas I blit a portion of the image on itself to keep the datas I need, and then blit the portion of the PCX I need.
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LuMo



Joined: 21 Aug 2005
Posts: 410
Location: Austria
PostPosted: Fri Jan 06, 2006 8:16 pm    Post subject: Reply with quote
only blit the really needed data, otherwise it really slows down...
480x272px more is never needed
greets
lumo
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