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Render NODATA as transparent and clip highbit data

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ala GDAL for greyscale outputs. Addresses #2661
This commit is contained in:
Paul Ramsey 2015-07-08 08:29:53 -07:00
parent 1c56214bbb
commit d144f97f4e
1 changed files with 14 additions and 2 deletions
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16
plugins/input/pgraster/pgraster_wkb_reader.cpp
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@ -271,18 +271,30 @@ mapnik::raster_ptr read_grayscale_band(mapnik::box2d<double> const& bbox,
int val;
int nodataval;
uint8_t * data = image.bytes();
int ps = 4; // sizeof(image::pixel_type)
int off;
val = reader(); // nodata value, need to read anyway
nodataval = reader(); // nodata value, need to read anyway
for (int y=0; y<height; ++y) {
for (int x=0; x<width; ++x) {
val = reader();
// Apply harsh type clipping rules ala GDAL
if ( val < 0 ) val = 0;
if ( val > 255 ) val = 255;
// Calculate pixel offset
off = y * width * ps + x * ps;
// Pixel space is RGBA
// Pixel space is RGBA, fill all w/ same value for Grey
data[off+0] = val;
data[off+1] = val;
data[off+2] = val;
// Set the alpha channel for transparent nodata values
// Nodata handling is *manual* at the driver level
if ( hasnodata && val == nodataval ) {
data[off+3] = 0x00; // transparent
} else {
data[off+3] = 0xFF; // opaque
}
}
}
mapnik::raster_ptr raster = std::make_shared<mapnik::raster>(bbox, image, 1.0);