[PATCH] Adds a transparent color index for handling empty CADRG subblocks

[Even Rouault]

Currently, NITFRasterBand::IReadBlock returns a block with color index 0 if there is no noDataValue (see code below). Unfortunatelly a lot of CADRG products (no to say all of them) do not define a transparent color. My patch consists in adding an extra color index for transparency if there is none in the product. Thus, empty subblocks will be displayed with this transparent color.

    else /* nBlockResult == BLKREAD_NULL */
    {
        if( psImage->bNoDataSet )
            memset( pImage, psImage->nNoDataValue,
                    psImage->nWordSize*psImage->nBlockWidth*psImage->nBlockHeight);
        else
            memset( pImage, 0,
                    psImage->nWordSize*psImage->nBlockWidth*psImage->nBlockHeight);

        return CE_None;
    }

[warmerdam]

Even,

This patch looks ok. Go ahead and apply it, but only in trunk. I don't want risky behavior changes in 1.4.3.

PS. please include "nitf" in keywords for all nitf driver bugs.

[Even Rouault]

Commited in trunk in r11906

[warmerdam]

In r11923 I changed this code to only add the transparent LUT entry if there is a LUT. Fixes test stream crash.