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KJB
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KJB
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Digital orthoquad buffer. More...
#include <dorthoquad.h>
Public Types | |
| typedef unsigned char | Pixel |
| a single pixel is a gray level 0-255 More... | |
Public Member Functions | |
| int | num_tiles_to_cover (int) const |
| Compute how many tiles are needed to cover X number of meters. More... | |
| DOrthoQuad (unsigned edge_length_pix=0) | |
| Construct a digital orthoquad image buffer; must be square. More... | |
| int | fill (const pt &) |
| Fill the array with image data roughly around a given point. More... | |
| int | refill (const pt &) |
| Like fill(), but force a download from the internet. More... | |
| char | select_tileset (char) |
| change the tileset "theme" – see themes in lib/topo/master.h More... | |
| long | left () const |
| Return the "easting" coordinate of the left edge of the DOQ. More... | |
| long | top () const |
| Return the "northing" coordinate of the top edge of the DOQ. More... | |
| char | zone () const |
| return UTM zone for the DOQ (which must lie entirely in a zone). More... | |
| size_t | width () const |
| Return the east-west size of the image, in meters. More... | |
| size_t | height () const |
| Return the north-south size of the image, in meters. More... | |
| bool | isReady () const |
| Returns true iff the array has been filled with image data. More... | |
| int | as_matrix (Int_matrix *) const |
| represent DOQ as a matrix of integers: row 0, col 0 is northwest More... | |
| kjb_c::Pixel | read_color (unsigned, unsigned) const |
| Read pixel RELATIVE TO current left,top settings (meters offset) More... | |
| kjb_c::Pixel | read_abs_color (long, long) const |
| Return color pixel at given UTM coordinates (zone assumed) More... | |
| Pixel | read (unsigned, unsigned) const |
| Read pixel RELATIVE TO current left,top settings (meters offset) More... | |
| Pixel | read_abs (long, long) const |
| Return pixel at given UTM coordinates (zone assumed) More... | |
| Pixel | read_abs (const pt &) const |
| Return pixel at given UTM coordinates. More... | |
| pt | center () const |
| Return UTM coordinates of the center of the DOQ. More... | |
| const kjb::Image & | debug_access_internal_image_buffer () const |
| access internal buffer, but with clunky name to discourage you More... | |
| float | meters_per_pixel () const |
| retrieve the number of meters per pixel for chosen imagery theme More... | |
Digital orthoquad buffer.
This class lets you build grayscale digital orthoquad images. You choose the size, and then you can "fill" it centered at a given UTM coordinate. This downloads the data for you; then you can read pixels out of the buffer at will. The "fill" process queries an on-disk cache, and if any desired tiles are absent, it will request the missing tiles over the internets.
Centering is approximate. There is a granularity of about 200 pixels; the resulting image can have an offset of about plus or minus 100 pixels in each direction. The best way to cope with centering jitter is to use the read_abs() method to read pixels into a matrix, instead of the as_matrix method.
Default tileset: aerial imagery at 1 meter per pixel resolution, i.e., the tileset coded AIR_1M in header file lib/topo/master.h. You can change the tileset with the select_tileset() method. This is a new method, and much of the code and documentation assumes a 1 meter per pixel resolution. But many other tilesets have a different resolution, and so the code might not work as expected or the documentation might be wrong for such tilesets. It is a (low-priority) work in progress to make the code and documentation consistent with the recent possibility for other resolutions.
| typedef unsigned char kjb::TopoFusion::DOrthoQuad::Pixel |
a single pixel is a gray level 0-255
| kjb::TopoFusion::DOrthoQuad::DOrthoQuad | ( | unsigned | edge_length_pix = 0 | ) |
Construct a digital orthoquad image buffer; must be square.
| int kjb::TopoFusion::DOrthoQuad::as_matrix | ( | Int_matrix * | doq | ) | const |
represent DOQ as a matrix of integers: row 0, col 0 is northwest
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inline |
Return UTM coordinates of the center of the DOQ.
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inline |
access internal buffer, but with clunky name to discourage you
| int kjb::TopoFusion::DOrthoQuad::fill | ( | const pt & | center | ) |
Fill the array with image data roughly around a given point.
Use fill() under ordinary circumstances, since it will make use of locally cached results.
3 Dec 2010: It's unbelievable that I'm only discovering this after 2 years working with this code, but I now think the resulting image is only ROUGHLY centered on the given location, with a granularity of one "tile" (an internal unit of image tranfer that I thought was encapsulated so that you, the client, would never have to know about it). A tile, at this writing, is 200 x 200 pixels, so the filled image could, I think, be offset from your specified center by plus or minus 100 pixels, in either axis.
Use the read_abs() method to avoid the above granularity.
| size_t kjb::TopoFusion::DOrthoQuad::height | ( | ) | const |
Return the north-south size of the image, in meters.
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inline |
Returns true iff the array has been filled with image data.
| long kjb::TopoFusion::DOrthoQuad::left | ( | ) | const |
Return the "easting" coordinate of the left edge of the DOQ.
| float kjb::TopoFusion::DOrthoQuad::meters_per_pixel | ( | ) | const |
retrieve the number of meters per pixel for chosen imagery theme
| int kjb::TopoFusion::DOrthoQuad::num_tiles_to_cover | ( | int | meters | ) | const |
Compute how many tiles are needed to cover X number of meters.
How many tiles does it take to cover a given number of (linear) meters? This will tell you. Basically it computes the "ceiling" of the length in meters, divided by tile size in meters.
| DOrthoQuad::Pixel kjb::TopoFusion::DOrthoQuad::read | ( | unsigned | xcoord, |
| unsigned | ycoord | ||
| ) | const |
Read pixel RELATIVE TO current left,top settings (meters offset)
| DOrthoQuad::Pixel kjb::TopoFusion::DOrthoQuad::read_abs | ( | long | abs_xcoord, |
| long | abs_ycoord | ||
| ) | const |
Return pixel at given UTM coordinates (zone assumed)
| abs_xcoord | UTM easting (in meters) in same zone as last fill. |
| abs_ycoord | UTM northing (in meters) in same zone as last fill. |
| Index_out_of_bounds | if the query is outside the buffer contents |
This is at absolute location (not relative to current left,top), conditioned on the current value of zone(). If you go out of bounds it will throw.
| DOrthoQuad::Pixel kjb::TopoFusion::DOrthoQuad::read_abs | ( | const pt & | p | ) | const |
Return pixel at given UTM coordinates.
| p | query location (absolute, not relative to current left,top) |
| Index_out_of_bounds | if the DOQ does not hold imagery at point p |
| kjb_c::Pixel kjb::TopoFusion::DOrthoQuad::read_abs_color | ( | long | abs_xcoord, |
| long | abs_ycoord | ||
| ) | const |
Return color pixel at given UTM coordinates (zone assumed)
| abs_xcoord | UTM easting (in meters) in same zone as last fill. |
| abs_ycoord | UTM northing (in meters) in same zone as last fill. |
| Index_out_of_bounds | if the query is outside the buffer contents |
This is at absolute location (not relative to current left,top). The zone for the coordinates is the same as that of the last fill command, but if you aren't sure what that was, just use the zone() method. If you go out of bounds it will throw.
| kjb_c::Pixel kjb::TopoFusion::DOrthoQuad::read_color | ( | unsigned | xcoord_m, |
| unsigned | ycoord_m | ||
| ) | const |
Read pixel RELATIVE TO current left,top settings (meters offset)
| int kjb::TopoFusion::DOrthoQuad::refill | ( | const pt & | center | ) |
| char kjb::TopoFusion::DOrthoQuad::select_tileset | ( | char | tileset | ) |
change the tileset "theme" – see themes in lib/topo/master.h
| long kjb::TopoFusion::DOrthoQuad::top | ( | ) | const |
Return the "northing" coordinate of the top edge of the DOQ.
| size_t kjb::TopoFusion::DOrthoQuad::width | ( | ) | const |
Return the east-west size of the image, in meters.
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inline |
return UTM zone for the DOQ (which must lie entirely in a zone).
1.8.6