Load image with GDAL Libraries (VC++) - c++

Question

I have a problem when I try to load an image with GDAL Libraries, and implements it(image) to the OpenGL Control. The problem is on the color as you can see on the picture.
And this is the functions to generate texture from the image:
GLuint COpenGLControl::ReadGDALData(CString filename)
{
BYTE* tempReturn;
GLuint texture;
GDALDataset *poDataset;
GDALAllRegister();
poDataset = (GDALDataset *) GDALOpen((const char *)(CStringA)filename, GA_ReadOnly);
int Height = poDataset->GetRasterXSize(), Width = poDataset->GetRasterYSize();
LONG LineBytes = (Width*8+31)/32*4;
BYTE * pData = (BYTE *)new char[ LineBytes * Height * 3];
if (poDataset == NULL)
{
AfxMessageBox("Couldn't open selected file!");
return NULL;
}
nBands = poDataset->GetRasterCount();
GDALRasterBand **poBand;
poBand = new GDALRasterBand *[nBands];
if (poBand == NULL)
{
AfxMessageBox("Couldn't open the bands!", MB_ICONWARNING);
return NULL;
}
for (int i=0; i<nBands; i++)
{
poBand[i] = poDataset->GetRasterBand(i+1);
if (poBand[i] == NULL)
{
AfxMessageBox("Couldn't open selected bands", MB_ICONWARNING);
return NULL;
}
}
int BandChoice = 2;
nXsize = poBand[BandChoice]->GetXSize();
nYsize = poBand[BandChoice]->GetYSize();
if (BandChoice == 1)
{
poBandBlock_Gray = (BYTE*)CPLMalloc(sizeof(BYTE)*(nXsize*nYsize));
poBand[BandChoice]->RasterIO(GF_Read, 0, 0, nXsize, nYsize, poBandBlock_Gray, nXsize, nYsize, poBand[BandChoice]->GetRasterDataType(), 0, 0);
}
else
{
int nXsize_R, nXsize_G, nXsize_B;
int nYsize_R, nYsize_G, nYsize_B;
int BandChoiceR = 0;
int BandChoiceG = 1;
int BandChoiceB = 2;
nXsize_R = poBand[BandChoiceR]->GetXSize();
nXsize_G = poBand[BandChoiceG]->GetXSize();
nXsize_B = poBand[BandChoiceB]->GetXSize();
nYsize_R = poBand[BandChoiceR]->GetYSize();
nYsize_G = poBand[BandChoiceG]->GetYSize();
nYsize_B = poBand[BandChoiceB]->GetYSize();
nXsize = nXsize_R;
nYsize = nYsize_R;
poBandBlock_R = (BYTE*)CPLMalloc(sizeof(BYTE)*(nXsize_R*nYsize_R));
poBandBlock_G = (BYTE*)CPLMalloc(sizeof(BYTE)*(nXsize_G*nYsize_G));
poBandBlock_B = (BYTE*)CPLMalloc(sizeof(BYTE)*(nXsize_B*nYsize_B));
poBand[BandChoiceR]->RasterIO(GF_Read, 0, 0, nXsize_R, nYsize_R, poBandBlock_R, nXsize_R, nYsize_R, poBand[BandChoiceR]->GetRasterDataType(), 0, 0);
poBand[BandChoiceG]->RasterIO(GF_Read, 0, 0, nXsize_G, nYsize_G, poBandBlock_G, nXsize_G, nYsize_G, poBand[BandChoiceG]->GetRasterDataType(), 0, 0);
poBand[BandChoiceB]->RasterIO(GF_Read, 0, 0, nXsize_B, nYsize_B, poBandBlock_B, nXsize_B, nYsize_B, poBand[BandChoiceB]->GetRasterDataType(), 0, 0);
delete poDataset;
}
if (BandChoice == 1)
{
for ( int i=0; i < Height; i++)
{
for ( int j=0; j < Width; j++)
{
pData[(Height-i-1) * LineBytes + j] = poBandBlock_Gray[i*Width + j];
}
}
CPLFree(poBandBlock_Gray);
}
else
{
int j2 ;
for ( int i=0; i<Height; i++)
{
for ( int j=0, j2=0; j < Width, j2 < 3 * Width; j++, j2+=3)
{
pData[(Height-i-1)*LineBytes + j2+2] = poBandBlock_R[i*Width + j];
pData[(Height-i-1)*LineBytes + j2+1] = poBandBlock_G[i*Width + j];
pData[(Height-i-1)*LineBytes + j2] = poBandBlock_B[i*Width + j];
}
}
CPLFree(poBandBlock_B);
CPLFree(poBandBlock_R);
CPLFree(poBandBlock_G);
}
// allocate a texture name
glGenTextures( 1, &texture );
// select our current texture
glBindTexture( GL_TEXTURE_2D, texture );
// select modulate to mix texture with color for shading
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );
// when texture area is small, bilinear filter the closest mipmap
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_LINEAR_MIPMAP_NEAREST );
// when texture area is large, bilinear filter the first mipmap
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
// if wrap is true, the texture wraps over at the edges (repeat)
// ... false, the texture ends at the edges (clamp)
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, FALSE );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, FALSE );
// build our texture mipmaps
gluBuild2DMipmaps( GL_TEXTURE_2D, 3, Width, Height, GL_RGB, GL_UNSIGNED_BYTE, pData );
// free buffer
free( pData );
return texture;
}
This is the Draw function:
void COpenGLControl::OnDraw(CDC *pDC)
{
// TODO: Camera controls
wglMakeCurrent(hdc,hrc);
// Set color to use when clearing the background.
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClearDepth(1.0f);
// Turn on backface culling
glFrontFace(GL_CCW);
glCullFace(GL_FRONT_AND_BACK);
// Turn on depth testing
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear all objects
glEnable( GL_TEXTURE_2D ); // enable texture for 2 dimensions
glPushMatrix();
if (filename.IsEmpty() == false)
{
imgData = ReadGDALData( filename );
glBindTexture( GL_TEXTURE_2D, imgData );
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear all objects
glLoadIdentity ();
gluLookAt (0,0,1,0,0,0,0,1,0);
glTranslatef (m_fPosX, m_fPosY, 0.0f);
glScalef (m_fZoom,m_fZoom,1.0);
glBegin( GL_QUADS ); // apply loaded texture to viewport
glTexCoord2d(0.0,0.0); glVertex2d(-1.0,-1.0);
glTexCoord2d(1.0,0.0); glVertex2d(+1.0,-1.0);
glTexCoord2d(1.0,1.0); glVertex2d(+1.0,+1.0);
glTexCoord2d(0.0,1.0); glVertex2d(-1.0,+1.0);
glEnd();
}
glPopMatrix();
glDisable( GL_TEXTURE_2D );
glFlush();
// Swap buffers
SwapBuffers(hdc);
wglMakeCurrent(NULL, NULL);
}

Answer 1

The problem is not so much in the color, but (from what I can tell from the sample) in the way your data is packed. Look into what byte ordering / row padding / color packing your OpenGL buffer expects, and in your GDAL loader what it provides. Just a hunch here, but it seems like your OpenGL expects a 4th (alpha) component in your RGB structs, but your GDAL code doesn't supply that. Also your GDAL loader aligns on 32 bit boundaries it seems, check if your OpenGL texture calls require that, too. Did you copy/paste the GDAL loader from a sample where somebody uses it to draw with BitBlt()? It looks that way.