Shulou(Shulou.com)06/03 Report--

7.1 description and analysis of built-in function parameters

Path storage is used to manage paths and draw complex graphics. You can add lines, curves, and other paths at will.

Header file

# include

Type definition

Typedef path_base path_storage

Basic member function

Move_to ()

Add the vertex with the command path_cmd_move_to, meaning the next line is drawn from this point

Line_to ()

Add the vertex whose command is path_cmd_line_to, meaning to draw a line to this point

Arc_to (double rx, double ry, double angle,bool large_arc_flag, bool sweep_flag, double x, double y)

Add an arc path, the axis length is rx, ry, the angle is angle, superior / inferior arc, clockwise, the end point is (xmemy).

Curve3_to ()

Add a Bezier curve with a parameter of a control point and the coordinates of the end point

Curve4_to ()

Add a Bezier curve with the parameters of two control points and the coordinates of the end point

Join_path ()

Add a vertex source, which is a combination

Vertex (unsigned idx, double* x, double* y)

Last_vertex (double* x, double* y)

Vertex (double* x, double* y)

Take the vertex position, the former is a known step, and the latter two are obtained sequentially or in reverse order

Modify_vertex ()

Modify_command ()

Modify vertex coordinates and commands for step idx

7.2 property modification of vertex source 1) flip according to Abscissa or ordinate

Description: there are many possible places for flip_y, which flips the Y axis.

/ / Flip all vertices horizontally or vertically

/ / between x1 and x2, or between y1 and y2 respectively

/ /-

Void flip_x (double x1, double x2)

Void flip_y (double Y1, double Y2)

2) comparison of simple examples

Ras.reset ()

Agg::path_storage path

Path.move_to (40350)

Path.line_to (80350)

Path.line_to (80670)

Path.line_to (40670)

Path.end_poly ()

Path.flip_y (350450)

Ras.add_path (path)

Agg::path_storage comparepath

Comparepath.move_to (140350)

Comparepath.line_to (180350)

Comparepath.line_to (180670)

Comparepath.line_to (140670)

Comparepath.end_poly ()

Ras.add_path (comparepath)

Agg::render_scanlines_aa_solid (ras,sl,renb,agg::rgba8 (255j0pl 0))

7.3 Line segment drawing rule figure 1) Hollow figure

Disclaimer: draw line segments in MFC, simply using MoveTo and LineTo, but path_storage using AGG must go through agg::conv_stroke (Show outline) to display line segments. Try annotating agg::conv_stroke to understand the basic operation flow.

Ras.reset ()

Agg::path_storage ps

Ps.move_to (200200)

Ps.line_to (400200)

Ps.line_to (400400)

Agg::conv_stroke

Stroke (ps)

Ras.add_path (stroke)

Agg::render_scanlines_aa_solid (ras,sl,renb,agg::rgba8 (255j0pl 0))

Ras.reset ()

2) solid graphics (with fill color)

Description: need to draw fill color graphics, must be closed, path_storage provides several closed functions, you can try to replace.

Ras.reset ()

Agg::path_storage ps

Ps.move_to (200200)

Ps.line_to (400200)

Ps.line_to (400400)

Ps.end_poly ()

Ras.add_path (ps)

Agg::render_scanlines_aa_solid (ras,sl,renb,agg::rgba8 (255j0pl 0))

Ras.reset ()

7.4 points for consideration

Path_storage allocates at least one block of memory to store 256vertex sources, so creating a large number of path_storage is quite

Expensive memory overhead and easy to cause memory fragmentation. It is recommended that a class hold a static member, through the function

Remove_all empties all vertex sources and start_new_path contains a new path, storing multiple paths in the

In an object. If you want to create a path_storage that contains many vertex sources, it is best to use vertex_block_storage.

If you want to create many path_storage but contain very small vertex sources, it is best to use vertex_stl_storage

Adapter.

Code description

M_coord_blocks saves coordinates

Instructions for m_cmd_blocks to save coordinates

Template

Inline unsigned vertex_block_storage::vertex (unsigned idx

Double* x, double* y) const

{

Unsigned nb = idx > > block_shift

/ / A block block stores 256 endpoint sources. Through idx > > 8, which packet is obtained?

Const T* pv = masked code _ blocks [nb] + ((idx & block_mask)

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