2D Sprite scaling

[LordNyson]

Hey there, I have been having a little bit of a hiccup for a while. Basically due to the ability to alter the resolution of the application I am designing I am getting a headache.

What is happening is I have got the restarting of the engine running fine, however, I have to scale the 2d GUI to the new resolution. I was given some code not too long ago, that scaled it for me, and have since.. I think... got my head around it, but there are still a few grey areas. The code itself, once you restarted the engine did not always work, and upon editing it, I find that every time I now restart the engine (by this I mean change resolution, press apply and it creates a new irrlicht window, in place of the old one) It gives me an error.

Here is my edited version:

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irr::video::ITexture* EngineElements::scaleTexture(irr::video::ITexture* SrcTexture, const irr::core::dimension2di& destSize, stringc image)
{ 
   ITexture* IntTexture = 0; 
   stringc SrcName = image; 

   IntTexture = driver->getTexture((image += (stringc)destSize.Width += (stringc)"x" += (stringc)destSize.Height += (stringc)".png").c_str()); 
   if(IntTexture != 0)return IntTexture;
 
   IImage* SrcImage = 0;
   IImage* DestImage = 0; 

   driver->setTextureCreationFlag(irr::video::ETCF_CREATE_MIP_MAPS, false); 

   try
   {
		IntTexture = driver->addTexture(destSize, "IntermediateTexture"); 
		SrcImage = driver->createImageFromData(SrcTexture->getColorFormat(), SrcTexture->getSize(), SrcTexture->lock()); 
		DestImage = driver->createImageFromData(SrcTexture->getColorFormat(), destSize, IntTexture->lock());   
   }
   catch(...)
   {
		int temp = MessageBox(NULL, ((stringc)"Error in scaling image: " += image += (stringc)"\nThis can be caused by incorrect resolution settings.").c_str(),"Fatal Error",MB_OK | MB_ICONSTOP);
		return NULL;
   };
   
   SrcTexture->unlock(); 
   SrcImage->copyToScaling(DestImage);
   IntTexture->unlock();

   driver->writeImageToFile(DestImage,(SrcName += (stringc)destSize.Width += (stringc)"x" += (stringc)destSize.Height += (stringc)".png").c_str());

   driver->removeTexture(IntTexture); 
   IntTexture = driver->addTexture(SrcName.c_str(), DestImage); 
   SrcImage->drop(); 
   DestImage->drop(); 

   driver->setTextureCreationFlag(irr::video::ETCF_CREATE_MIP_MAPS, true);  
   
   return IntTexture; 
}  

Here is the given code:

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irr::video::ITexture* Game::scaleTexture(irr::video::ITexture* SrcTexture, const irr::core::dimension2di& destSize) const 
{ 
   static irr::u32 counter = 0; 
   irr::video::IImage* SrcImage = 0; 
   irr::video::IImage* DestImage = 0; 
   irr::video::ITexture* IntTexture = 0; 
   irr::core::stringc SrcName = "NewTexture"; 
   SrcName += counter; 

   videoDriver->setTextureCreationFlag(irr::video::ETCF_CREATE_MIP_MAPS, false); 

   IntTexture = this->videoDriver->addTexture(destSize, "IntermediateTexture"); 
   SrcImage = this->videoDriver->createImageFromData(SrcTexture->getColorFormat(), SrcTexture->getSize(), SrcTexture->lock()); 
   DestImage = this->videoDriver->createImageFromData(SrcTexture->getColorFormat(), destSize, IntTexture->lock()); 

   IntTexture->unlock(); 
   SrcImage->copyToScaling(DestImage); 
   SrcTexture->unlock(); 

   this->videoDriver->removeTexture(IntTexture); 
   IntTexture = this->videoDriver->addTexture(SrcName.c_str(), DestImage); 
   SrcImage->drop(); 
   DestImage->drop(); 

   videoDriver->setTextureCreationFlag(irr::video::ETCF_CREATE_MIP_MAPS, true); 

   ++counter; 

   return IntTexture; 
} 

I have a question regarding:

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  DestImage = driver->createImageFromData(SrcTexture->getColorFormat(), destSize, IntTexture->lock());   

I experimented with that line a great deal and was wondering why using:

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createImage(ECF_A8R8G8B8, destSize)

wouldn't that make a blank image? how does using a texture of a different resolution work and a blank one doesn't?

Also, yes it does produce a file name in this format: AMIBackground2.png800x600.png

[DavidJE13]

the code isn't too complex - ignoring the beginning setup,

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IntTexture = this->videoDriver->addTexture(destSize, "IntermediateTexture");

Create a texture with the destination size. We already have SrcTexture which is the input texture.

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   SrcImage = this->videoDriver->createImageFromData(SrcTexture->getColorFormat(), SrcTexture->getSize(), SrcTexture->lock());
   DestImage = this->videoDriver->createImageFromData(SrcTexture->getColorFormat(), destSize, IntTexture->lock());

Create images from these textures - these images are *exactly* the same size as their textures. BlahTexture->lock() gives it a reference to the bytedata of the textures to initialise with. Your code omitting this bit doesn't work because it has no data to start with, and there is no stretching going on here.

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IntTexture->unlock();
   SrcImage->copyToScaling(DestImage);
   SrcTexture->unlock();

Here's the magic line! The destination image becomes a scaled version of SrcImage, and both textures are unlocked (always call unlock after a call to lock)

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this->videoDriver->removeTexture(IntTexture);
   IntTexture = this->videoDriver->addTexture(SrcName.c_str(), DestImage);

finally IntTexture is re-allocated. now it has size of the destination, and is set with the new scaled image data.

Not the most efficient function - "Intermediate Texture" is just wasted space, and it's using a static variable as a counter (to ensure each new texture has a unique name), which isn't the best practice.

As for your code, I see no blatant error; maybe you're calling it with the same image name twice? or running out of vram?

[LordNyson]

Basically there are two errors, if we don't get an error here =:

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   try
   {
		IntTexture = driver->addTexture(destSize, "IntermediateTexture"); 
		SrcImage = driver->createImageFromData(SrcTexture->getColorFormat(), SrcTexture->getSize(), SrcTexture->lock()); 
		DestImage = driver->createImageFromData(SrcTexture->getColorFormat(), destSize, IntTexture->lock());   
   }
   catch(...)
   {
		int temp = MessageBox(NULL, ((stringc)"Error in scaling image: " += image += (stringc)"\nThis can be caused by incorrect resolution settings.").c_str(),"Fatal Error",MB_OK | MB_ICONSTOP);
		return NULL;
   };

Which is fairly common, it will drop out into the main game loop and get an error when

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  gi->drawAll();

is called.

Really the only thought I have is that the dimensions being passed are invalid, so when the texture is returned and tried to be applied it screws up. But I have checked the debug data, it passes correct values, and you can tell that by the filename too...