Magick Pixel data garbled after minify - c++

Question

I need to read in images of arbitrary sizes and apply them to GL textures. I am trying to resize the images with ImageMagick to get them to fit inside a maximum 1024 dimension texture.
Here is my code:
Magick::Image image(filename);
int width = image.columns();
int height = image.rows();
cout << "Image dimensions: " << width << "x" << height << endl;
// resize it to fit a texture
while ( width>1024 || height>1024 ) {
try {
image.minify();
}
catch (exception &error) {
cout << "Error minifying: " << error.what() << " Skipping." << endl;
return;
}
width = image.columns();
height = image.rows();
cout << " -- minified to: " << width << "x" << height << endl;
}
// transform the pixels to something GL can use
Magick::Pixels view(image);
GLubyte *pixels = (GLubyte*)malloc( sizeof(GLubyte)*width*height*3 );
for ( ssize_t row=0; row<height; row++ ) {
Magick::PixelPacket *im_pixels = view.get(0,row,width,1);
for ( ssize_t col=0; col<width; col++ ) {
*(pixels+(row*width+col)*3+0) = (GLubyte)im_pixels[col].red;
*(pixels+(row*width+col)*3+1) = (GLubyte)im_pixels[col].green;
*(pixels+(row*width+col)*3+2) = (GLubyte)im_pixels[col].blue;
}
}
texPhoto = LoadTexture( pixels, width, height );
free(pixels);
The code for LoadTexure() looks like this:
GLuint LoadTexture(GLubyte* pixels, GLuint width, GLuint height) {
GLuint textureId;
glPixelStorei( GL_UNPACK_ALIGNMENT, 1 );
glGenTextures( 1, &textureId );
glBindTexture( GL_TEXTURE_2D, textureId );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, (unsigned int*)pixels );
return textureId;
}
All the textures work great except when they have had image.minify() applied to them. Once minified the pixels are basically just random noise. There must be something else going on that I'm not aware of. I am probably missing something in the ImageMagick docs about what I am supposed to do to get the pixel data after I minify it.
How do I properly get the pixel data after a call to minify()?

Answer 1

It turns out that the problem was in the libraries and has to do with the environment I'm running in which is on a Raspberry Pi embedded system. Maybe just a recompile of the sources would have been sufficient but for my purposes I decided I should also reduce the quantum size to 8 bits rather than Magick's default of 16. I also chose a few other configure options for my scenario.
It basically boiled down to this:
apt-get remove libmagick++-dev
wget http://www.imagemagick.org/download/ImageMagick.tar.gz
tar xvfz ImageMagick.tar.gz
cd IMageMagick-6.8.7-2
./configure --with-quantum-depth=8 --disable-openmp --disable-largefile --without-freetype --without-x
make
make install
And then compile against these libraries instead. I also needed to make soft links in /usr/lib to the so files.