Displaying image with OpenGL and DevIL in C?
Post: #1
how to display image with OpenGL and DevIL? Or is this not possible, and I must use libs like libPNG instead?
This code doesn't do anything. Not surprisingly..
and then I tried using textures...
This code manages to turn every shape's colour in the screen to the most predominant colour in the image. I was trying to do it with textures.
Code:
ilutGLLoadImage("/Users/eric/GLExperiment/Images/fighter.png");
glDrawPixels(64,64,GL_RGB,GL_UNSIGNED_BYTE,ilGetData);This code doesn't do anything. Not surprisingly..
and then I tried using textures...
Code:
ilutGLLoadImage("/Users/eric/GLExperiment/Images/fighter.png");
ilGenImages (1, &ImgId);
ilBindImage (ImgId);
glEnable (GL_TEXTURE_2D);
glBindTexture (GL_TEXTURE_2D, TexID);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, Width, Height, 0, GL_RGB, GL_UNSIGNED_BYTE, ilGetData);
glBegin (GL_QUADS);
glTexCoord2f (X1, Y1);// glVertex3i (0, 0, 0);
glVertex2f(X1, Y1);
glTexCoord2f (X1+Width,Y1);// glVertex3i (Width, 0, 0);
glVertex2f(X1+Width, Y1);
glTexCoord2f (X1+Width,Y1+Height);// glVertex3i (Width, Height, 0);
glVertex2f(X1+Width, Y1+Height);
glTexCoord2f (X1, Y1+Height);// glVertex3i (0, Height, 0);
glVertex2f(X1,Y1+Height);
glEnd();This code manages to turn every shape's colour in the screen to the most predominant colour in the image. I was trying to do it with textures.
Post: #2
The texture coordinates should go from 0 to 1. So where you have glTexCoord2f(X1, Y1), you should have glTexCoord2f(0, 0). Also, in place of glVertex2f(X1 + Width, Y1 + Height), you should have glVertex2f(1, 1). I'm sure you can figure out the rest. 
Post: #4akb825 Wrote:The texture coordinates should go from 0 to 1. So where you have glTexCoord2f(X1, Y1), you should have glTexCoord2f(0, 0). Also, in place of glVertex2f(X1 + Width, Y1 + Height), you should have glVertex2f(1, 1). I'm sure you can figure out the rest.
I did that thing OneSadCookie told me in his tutorial. -> make the coordinate system measure interms of pixels instead of the default system. I still use the coordinates you told me
OneSadCookie Wrote:and I'm sure ilGetData is a function, not a global variable!
Its a function, I can use it like this, right? It gets the memory address of the image I loaded, and returns it as a pointer.
Post: #6OneSadCookie Wrote:Function calls in C always have parentheses.
>.> Why didn't it give me an error?
Post: #8
I put the parenthesis in, now all the rectangles and lines on my app flash green blue and red, make my head dizzy.. >< But I still don't see any image! Note that I am able to get data about the image, eg. its width and height, so I am sure I have it loaded into the app.
Code:
'see other posts. deleted for space.
Post: #9
You still haven't changed the texture coordinates. Having the coordinate system match up pixel by pixel works with the vertex coordinates, but not the texture coordinates. Like I said earlier, they go from 0 to 1: always. (unless you are using GL_TEXTURE_RECTANGLE_EXT/ARB instead of GL_TEXTURE_2D, but that's the only exception) Also, you can't just say "TexID = 2". You have to call glGenTextures first.
Post: #10akb825 Wrote:Also, you can't just say "TexID = 2". You have to call glGenTextures first.
Unfortunately, you're wrong about that. You *can* choose your own texture IDs, and OpenGL just has to deal. This is something that they will fix for OpenGL LM / OpenGL 3.0. You're right, though, that you *should* call GenTextures.
leRiCi, isn't there a DevIL function that does the TexImage2D for you?
Post: #11
There is, but the example containing the command won't compile. Anyways... I realised I posted the wrong version of the code I had. Here, I called GenTextures and didn't declare my TexID and changed the texture coordinates and used the GL command for DevIL. Now it doesn't do anything at all. ><
Code:
// GL texture ID
GLuint TexID;
// IL image ID
ILuint ImgId;
ILboolean success;
ilGenImages (1, &ImgId);
ilBindImage (ImgId);
success = ilLoadImage("/Users/eric/GLExperiment/Images/fighter.png");
if (success)
{
success= ilConvertImage(IL_RGB,IL_UNSIGNED_BYTE);
if (!success)
{
}
glGenTextures(1, &TexID);
glBindTexture(GL_TEXTURE_2D, TexID);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); /* We will use linear
interpolation for magnification filter */
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); /* We will use linear
interpolation for minifying filter */
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()); /* Texture specification */
}
else
{
}
int Width = ilGetInteger (IL_IMAGE_WIDTH);
int Height = ilGetInteger (IL_IMAGE_HEIGHT);
glBegin(GL_QUADS);
glTexCoord2i(0, 0); glVertex2i(X1, Y1);
glTexCoord2i(0, 1); glVertex2i(X1, Y1+Height);
glTexCoord2i(1, 1); glVertex2i(X1+Width, Y1+Height);
glTexCoord2i(1, 0); glVertex2i(X1+Width, Y1);
glEnd();
Post: #12
What's the value of X1 and Y1? Are you trying to give the value of the window's x and y? If so, don't. Assuming you correctly set up the orthographic matrix (for example, with glOrtho(0, width, 0, height, 1, -1)) and viewport (for example, glViewport(0, 0, width, height)), the viewable coordinates should be 0-width for the x and 0-height for the y.
Post: #13
I want to put my head in the toilet and flush it away.... I called this function before glClear.... *sigh* It probably had always been working, and I was just wasting my time. Sorry guys. but thanks.
Post: #14leRiCl Wrote:I want to put my head in the toilet and flush it away.... I called this function before glClear.... *sigh* It probably had always been working, and I was just wasting my time. Sorry guys. but thanks.
No sweat. I did the same thing yesterday. I was pulling my hair out trying to figure out why my screen was blank.
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