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POopenGL texturing shows only red component of texture
 

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  1. POopenGL texturing shows only red component of texture
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    <p>I am trying to texture map an image to a single polygon. My image is being read correctly, but only the red plane of the image is being textured.</p> <p>I am doing this within a QGLWidget </p> <p>I have checked the image after it is read, and it's components are being read correctly--ie, I get valid values for the green and blue planes.</p> <p>Here is the code</p> <p><code> </p> <pre><code>QImageReader *theReader = new QImageReader(); theReader-&gt;setFileName(imageFileName); QImage theImageRead = theReader-&gt;read(); if(theImageRead.isNull()) { validTile = NOT_VALID_IMAGE_FILE; return; } else { int newW = 1; int newH = 1; while(newW &lt; theImageRead.width()) { newW *= 2; } while(newH &lt; theImageRead.height()) { newH *= 2; } theImageRead = theImageRead.scaled(newW, newH, Qt::IgnoreAspectRatio, Qt::SmoothTransformation); // values checked in theImageRead are OK here glGenTextures(1,&amp;textureObject); theTextureImage = QGLWidget::convertToGLFormat(theImageRead); // values checked in theTextureImage are OK here glBindTexture(GL_TEXTURE_2D, textureObject); glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,newW, newH, 0, GL_RGBA, GL_UNSIGNED_BYTE,theTextureImage.bits() ); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR); glFlush(); validTile = VALID_TEXTURE; return; } </code></pre> <p></p> <p>then I draw like this:</p> <p><code></p> <pre>{ glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D,textureTiles[tN]-&gt;getTextureObject() ); glBegin(GL_QUADS); glTexCoord2f(0.0,0.0); glVertex2f(textureTiles[tN]-&gt;lowerLeft.x(), textureTiles[tN]-&gt;lowerLeft.y()); glTexCoord2f(1.0,0.0); glVertex2f(textureTiles[tN]-&gt;lowerRight.x(), textureTiles[tN]-&gt;lowerRight.y()); glTexCoord2f(1.0,1.0); glVertex2f(textureTiles[tN]-&gt;upperRight.x(), textureTiles[tN]-&gt;upperRight.y()); glTexCoord2f(0.0,1.0); glVertex2f(textureTiles[tN]-&gt;upperLeft.x(), textureTiles[tN]-&gt;upperLeft.y()); glEnd(); glDisable(GL_TEXTURE_2D); } </code></pre> <p></code></p> <p>Does anybody see anything that would cause my texture to be interpreded as if it is values of (r,0,0,1)? (r,g,b,a)?</p> <p>QT 4.7.1, Ubuntu 10.04, openGl 2.something or other</p> <p>thanks in advance for any help</p>
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    1. USjhowland
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    1. CODo you have a `glColor()` call somewhere that you forgot about?
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    2. COInternally, OpenGL takes the internalFormat parameter and applies whatever required calculations to your data to get it in the requested format. The result of this (if I understand the docs correctly) is always an RGBA image as far as GL is concerned. What happens if, for testing purposes, you explicitly set the internalFormat to GL_RGBA instead of GL_RGB in the function call?
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    3. COnothing--no difference at all
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