Is this me or Allegro?!? http://www.allegro.cc/forums/view/615293 Allegro.cc Forum Thread matthew@allegro.cc (Matthew Leverton) Wed, 15 Apr 2015 21:19:51 +0000

I'm trying to scale images to a temp buffer and then draw that image to the screen. The base image is a huge image of sprites that are 16x32. I'm using the following code to draw the individual sprites, but the destination is not correct and seems to be based on the scale factor. I'm sure I'm just missing something stupid but can't seem to see it at the moment. Any help would be appreciated. I'm using allegro-5.0.10 if that helps at all...

#SelectExpand
1bool DrawTerrainImage( ALLEGRO_BITMAP *terrainImage, float x, float y, 2 int terrainID, unsigned char scaleFactor ) 3{ 4 // TODO: add bounds handlers for known end points. 5 int dw = 16*scaleFactor; 6 int dh = 32*scaleFactor; 7 ALLEGRO_BITMAP *temp = al_create_bitmap(dw,dh); 8 if ( !temp ) 9 return false; 10 ALLEGRO_STATE state; 11 al_store_state(&state,ALLEGRO_STATE_TARGET_BITMAP); 12 al_set_target_bitmap(temp); 13 // image, sx, sy, sw, sh, dx, dy,dw,dh, flags 14 al_draw_scaled_bitmap(terrainImage,16*terrainID, 0, 16, 32, 0, 0, dw, dh,0); 15 al_restore_state(&state); 16 al_draw_bitmap(temp,x,y,0); 17 al_destroy_bitmap(temp); 18 temp = NULL; 19 return true; 20} 21///////////////////////////////////////////////////////////////////////////////

]]> no-reply@allegro.cc (Don Freeman) Wed, 15 Apr 2015 11:50:08 +0000

Does this compute??

unsigned char scaleFactor

// I think the char should at least be converted to int or double

int dw = 16*scaleFactor;

]]> no-reply@allegro.cc (#00JMP00) Wed, 15 Apr 2015 14:09:39 +0000

Why? Could you imagine a case where you'd want to scale a 16x32 pixel sprite more than 255 times!?
Edit:
As an example, here is the command to draw and then the output... 

   DrawTerrainImage(terrain,10,10,5,10);
   DrawTerrainImage(terrain,200,200,16,5);

{"name":"609380","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/d\/1\/d1fb89476a9b8f2e340ca30bbf83da14.jpg","w":400,"h":400,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/d\/1\/d1fb89476a9b8f2e340ca30bbf83da14"}609380

Edit:
Nevermind. ::) I feel dumb hahaha. I forgot that half y of the image is transparent on most of the sprites, so it just looked off by that much. I'll probably store these all in a structure during loading so I don't have to do stretching every draw cycle. Thanks all.

]]> no-reply@allegro.cc (Don Freeman) Wed, 15 Apr 2015 20:03:59 +0000

For one, I would do some input validation to be sure the problem is actually located in your function.

Is this C or C++?

I would check to verify in a debugger or with printf, that the values you're giving are all correct before they hit an Allegro function.

Then, I'd make sure all of my Allegro/OpenGL transformations are set up correctly. Actually, that most definitely sounds like the problem if you're scaling AND THEN translating, obviously you won't get what you intend. It could also be a bug in that function, and I would check an Allegro 5 example that uses the function to see if it exhibits the same behavior.

[edit]

Don Freeman said:

Edit:
Nevermind. ::) I feel dumb hahaha. I forgot that half y of the image is transparent on most of the sprites, so it just looked off by that much. I'll probably store these all in a structure during loading so I don't have to do stretching every draw cycle. Thanks all.

Ah.

]]> no-reply@allegro.cc (Chris Katko) Wed, 15 Apr 2015 21:10:29 +0000

Yeah, I'm gonna clear the image to black during testing so I can see the edges of the images so something stupid like this doesn't happen again. ;)

]]> no-reply@allegro.cc (Don Freeman) Wed, 15 Apr 2015 21:19:51 +0000