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setpixel?

 
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Pappons



Joined: 18 Jul 2008
Posts: 2
Location: Copenhagen, Denmark
PostPosted: Wed Sep 29, 2010 2:21 pm    Post subject: setpixel? Reply with quote
Hi guys,

I see there's a getpixel() function in the module arc.graphics.routines - but what about setpixel() ie. a function to write a pixel to a texture in memory?

I tried rolling my own:

Code:

void SetPixel ( SDL_Surface* pSurface , Uint32 col , int x , int y )
{

   if ( SDL_MUSTLOCK ( pSurface ) )
   {
      SDL_LockSurface( pSurface ) ;
   }

   //determine position
   char* pPosition = cast( char* ) pSurface.pixels ;
   
   //offset by y
   pPosition += ( pSurface.pitch * y ) ;
   
   //offset by x
   pPosition += ( pSurface.format.BytesPerPixel * x ) ;
   
   //copy pixel data
   * pPosition = col ;

   if ( SDL_MUSTLOCK ( pSurface ) )
   {
      SDL_UnlockSurface( pSurface ) ;
   }
}


But it's not working - has anyone got any ideas? Smile

(on a side note, i'm trying to draw on top of a texture i used with my getpixel() test - getpixel works fine, by the way!)
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SirAlaran



Joined: 19 Feb 2007
Posts: 84
Location: Silicon Valley
PostPosted: Wed Sep 29, 2010 8:40 pm    Post subject: Re: setpixel? Reply with quote
Code:

uint* pixels = cast(uint*)(pSurface.pixels);
pixels[(y * pSurface.w) + x] = col;


This code assumes a 32-bit color depth for pSurface. Also keep in mind that when you modify the SDL_Surface the changes are not automatically uploaded to the graphics card memory. Arc uses OpenGL for the actual drawing. I think the updateTexture should do that.

Also, D has byte and ubyte types. Use those when you need a byte. char is for characters.

Pappons wrote:
Hi guys,

I see there's a getpixel() function in the module arc.graphics.routines - but what about setpixel() ie. a function to write a pixel to a texture in memory?

I tried rolling my own:

Code:

void SetPixel ( SDL_Surface* pSurface , Uint32 col , int x , int y )
{

   if ( SDL_MUSTLOCK ( pSurface ) )
   {
      SDL_LockSurface( pSurface ) ;
   }

   //determine position
   char* pPosition = cast( char* ) pSurface.pixels ;
   
   //offset by y
   pPosition += ( pSurface.pitch * y ) ;
   
   //offset by x
   pPosition += ( pSurface.format.BytesPerPixel * x ) ;
   
   //copy pixel data
   * pPosition = col ;

   if ( SDL_MUSTLOCK ( pSurface ) )
   {
      SDL_UnlockSurface( pSurface ) ;
   }
}


But it's not working - has anyone got any ideas? Smile

(on a side note, i'm trying to draw on top of a texture i used with my getpixel() test - getpixel works fine, by the way!)

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Pappons



Joined: 18 Jul 2008
Posts: 2
Location: Copenhagen, Denmark
PostPosted: Thu Sep 30, 2010 10:44 am    Post subject: Reply with quote
Wonderful - thanks for your quick reply! Smile

Now the setpixel works and looks great as well:
Code:
/**
   Sets a 32bit color pixel in the texture memory
*/
void setpixel32( Texture t , uint x , uint y , Color c )
{
   updateTexture(t, Point(x,y), Size(1,1), cast( ubyte[] ) [c.r,c.g,c.b,c.a] );
}
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mutable



Joined: 22 Jun 2010
Posts: 87
PostPosted: Thu Sep 30, 2010 4:37 pm    Post subject: Reply with quote
The SDL_Lock and -Unlock Operations are predestinated for the in/out block.
Just as a little tip.
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SirAlaran



Joined: 19 Feb 2007
Posts: 84
Location: Silicon Valley
PostPosted: Thu Sep 30, 2010 8:16 pm    Post subject: Reply with quote
mutable wrote:
The SDL_Lock and -Unlock Operations are predestinated for the in/out block.
Just as a little tip.


http://www.digitalmars.com/d/1.0/dbc.html wrote:
The assert's in the in and out bodies are called contracts. Any other D statement or expression is allowed in the bodies, but it is important to ensure that the code has no side effects, and that the release version of the code will not depend on any effects of the code. For a release build of the code, the in and out code is not inserted.


It is a much better idea to use the scope statement for such things, as the contracts are not present when you pass the -release switch to the compiler.
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mutable



Joined: 22 Jun 2010
Posts: 87
PostPosted: Fri Oct 01, 2010 7:53 am    Post subject: Reply with quote
SirAlaran wrote:
mutable wrote:
The SDL_Lock and -Unlock Operations are predestinated for the in/out block.
Just as a little tip.


http://www.digitalmars.com/d/1.0/dbc.html wrote:
The assert's in the in and out bodies are called contracts. Any other D statement or expression is allowed in the bodies, but it is important to ensure that the code has no side effects, and that the release version of the code will not depend on any effects of the code. For a release build of the code, the in and out code is not inserted.


It is a much better idea to use the scope statement for such things, as the contracts are not present when you pass the -release switch to the compiler.

You mean
Code:

scope(exit) {
    SDL_UnlockSurface(pSurface);
}

or?
But which scope Block can i use for the lock command?

But thanks, i don't know before, that the -release switch turns contracts off Smile But i love the in and out blocks for methods Smile
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SirAlaran



Joined: 19 Feb 2007
Posts: 84
Location: Silicon Valley
PostPosted: Fri Oct 01, 2010 7:50 pm    Post subject: Reply with quote
mutable wrote:

or?
But which scope Block can i use for the lock command?

But thanks, i don't know before, that the -release switch turns contracts off Smile But i love the in and out blocks for methods Smile


Code:

import std.stdio;

void unlock() {
   writeln("unlocking");
}

void lock() {
   writeln("locking");
}

void process() {
   writeln("process");
}

void theFunction(bool needsLocking) {
   if (needsLocking) lock();
   scope(exit) if(needsLocking) unlock();
   process();
}

void main(string[] args)
{
   theFunction(true);
   writeln("------");
   theFunction(false);
}

stdout wrote:

locking
process
unlocking
------
process

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SirAlaran



Joined: 19 Feb 2007
Posts: 84
Location: Silicon Valley
PostPosted: Sat Oct 02, 2010 5:09 pm    Post subject: Reply with quote
I've added direct pixel access as a feature to Arclib 2. It can be used like this:
Code:
// Disables drawing with this texture until endPixelAccess is called
texture.beginPixelAccess();
for(uint i = 0; i != 20; ++i)
{
   // Write pixels
   texture.setPixel(i, 16, Color(0xff00ffff));
}
// Ends pixel access mode and copies pixel data to OpenGL.
texture.endPixelAccess();


http://www.dsource.org/projects/arclib/browser/branches/arc2-alpha/arc/graphics/texture.d
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