initial image_data_any implentation (work-in-progress)
gdal - read single band as image_data_float32
(scaling/compositing FIXME)
add support for agg_pixfmt_gray32(_pre) and port changes to agg_color_gray/rgba and gamma calc from https://github.com/pelson/antigrain
gdal : experimenting with fetching gray scale single band as image_data_float32
remove duplicate/uneeded mapnik::raster ctor
fix compile of pgraster plugin
fix visibility of mapnik::composite function to python bindings - refs #2587
move image_data_any into seprate header
add image_data_null which is cheap to construct (no mem alloc)
add default ctor to image_data_any -> image_data_null
add to image_reader and implement empty (placeholder)
```image_data_any read(unsigned x, unsigned y, unsigned width, unsigned height) final```
in png/jpeg/webp/tiff readers
initial image_data_any read(...) implementation - always read into image_data_32
use new image_reader API
update visual test images after agg rgba improvements
read single band as int16 then agg_scale and colorize in gray16 color space, output rgb8 (aka image_data_32)
NOTE: proof-of-concept needed re-factoring/duplicate code removal
update a few expected images
update a few expected images
Merge branch 'master' of github.com:mapnik/mapnik into image_data_any
update agg blending cpp test - refs #1452
update expected visual test images
work in progress: start enhancing tiff reader to handle bits per sample