DevIL Importing TGA with Alpha Channel Error

Graphics and GPU Programming Programming OpenGL

Started by iwoplaza June 01, 2012 05:59 AM

5 comments, last by iwoplaza 11 years, 10 months ago

174

Author

June 01, 2012 05:59 AM

I am working on a RPG game in C + + and OpenGL. I am Importing TGA images, using Devil library. I am trying to import an image with alpha channel, but in my game the image is displayed with a black background

. Can you help me with this?

This is my code for importing alpha image:



GLuint loadAlphaTexture(const ILstring filename) {

	  ILuint texid;

	  ILboolean success;

	  GLuint image;

	  int finished;

	  ilInit();

	  ilGenImages(1, &texid);

	  ilBindImage(texid);

	  success = ilLoadImage(filename);

	  if (success)

	  {

	    success = ilConvertImage(IL_RGBA, IL_UNSIGNED_BYTE);

	    glGenTextures(1, &image);

	    glBindTexture(GL_TEXTURE_2D, image);

	    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

	    glTexImage2D(GL_TEXTURE_2D, 0, ilGetInteger(IL_IMAGE_BPP), ilGetInteger(IL_IMAGE_WIDTH),

	    ilGetInteger(IL_IMAGE_HEIGHT), 0, ilGetInteger(IL_IMAGE_FORMAT), GL_UNSIGNED_BYTE,ilGetData());

	  }

return image;

}

szecs

2,990

June 01, 2012 06:08 AM

Are you sure it's not a fault in your rendering function?
Are you sure it's not a fault on the image editing/saving side? Photohsohop 7.0 can't even save TGA with alpha without a plugin.

Why do you need this line?

[font=courier new,courier,monospace]ilConvertImage(IL_RGBA, IL_UNSIGNED_BYTE);[/font]

Your code looks okay anyway.

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iwoplaza

174

Author

June 01, 2012 06:38 AM

I'm saving images with GIMP. It's saving alpha channel.

My rendering func:



void DrawQuad(float x, float y,float z,float width,float height,float r,float g,float b,int tex){

	    glPushMatrix();

		    glLoadIdentity();

		    glColor3f(r, g, b);

		    glEnable(GL_TEXTURE_2D);

		 glBindTexture(GL_TEXTURE_2D, tex);

		 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

		 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

		    glBegin(GL_QUADS);

			    glTexCoord2f(0, 1);

			    glVertex3f(x, y,z);

			    glTexCoord2f(0, 0);

			    glVertex3f(x,y+height,z);

			    glTexCoord2f(1, 0);

			    glVertex3f(x+width, y+height,z);

			    glTexCoord2f(1, 1);

			    glVertex3f(x+width, y,z);

		    glEnd();

		    glDisable(GL_TEXTURE_2D);

	    glPopMatrix();	  

}

szecs

2,990

June 01, 2012 06:46 AM

Do you enable blending?
How you you set up your blending function?
[font=courier new,courier,monospace]glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA)[/font] is the usual way to achieve what you want.
Also, do you set up a rendering environment explicitly (though it shouldn't be a problem, as it's [font=courier new,courier,monospace]GL_MODULATE[/font] by default, if I recall correctly)?
What does [font=courier new,courier,monospace]ilConvertImage(IL_RGBA, IL_UNSIGNED_BYTE)[/font] do?

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iwoplaza

174

Author

June 01, 2012 06:58 AM

[color=#000000][font=verdana]llConvertImage converts the current bound image from its format/type to variables. You have full description here:[/font]http://www-f9.ijs.si...L/il/f00016.htm
[color=#000000][font=verdana]I don't use glBlendFunc.[/font]

szecs

2,990

June 01, 2012 07:02 AM

If you don't use [font=courier new,courier,monospace]glBlendfunc[/font], then you probably don't enable blending either ([font=courier new,courier,monospace]glEnable(GL_BLEND);[/font])
Which means you won't have blending, which means the alpha channel of your image is ignored.

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iwoplaza

174

Author

June 01, 2012 07:06 AM

O.o Thanks. That works

DevIL Importing TGA with Alpha Channel Error

[color=#000000][font=verdana]llConvertImage converts the current bound image from its format/type to variables. You have full description here:[/font]http://www-f9.ijs.si...L/il/f00016.htm
[color=#000000][font=verdana]I don't use glBlendFunc.[/font]

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DevIL Importing TGA with Alpha Channel Error

[color=#000000][font=verdana]llConvertImage converts the current bound image from its format/type to variables. You have full description here:[/font]http://www-f9.ijs.si...L/il/f00016.htm [color=#000000][font=verdana]I don't use glBlendFunc.[/font]

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[color=#000000][font=verdana]llConvertImage converts the current bound image from its format/type to variables. You have full description here:[/font]http://www-f9.ijs.si...L/il/f00016.htm
[color=#000000][font=verdana]I don't use glBlendFunc.[/font]