minigui-docs/programming-guide/MiniGUIProgGuidePart3Chapter04.md

mGPlus Programming

---+Basic concept introduction

mGPlus is a MiniGUI component which provides support for advanced graphics functions like path, gradient, anti-aliase stretch, and color combination. mGPlus is like GDI+ of Win32 or Cario.mGPlus will provide a series of interfaces to implement these functions. The library allows applications to draw graphics that do not need to be associated with device handles, that is, applications can create applications for stand-alone devices.

• Path: It consists of a group of strictly ordered polylines and curves. Use the path for filling and cutting.
• Color Gradient: refers to a brush that provides a color linear gradient or path gradient. This gradient brush can be used to fill areas, path areas, and graphics. Gradient brushes can also be used to draw lines, curves, and paths.
• Color Combination: The color combination determines the color values of the source, bottom, and intersection areas according to the combination rule.

Introduction of pen

Pen is used to draw lines, curves, and outlines of shapes. They are based on point-painting mechanisms. In addition to the common color and width attributes, the brush also has properties such as alignment, caps, and transitions.

Brush introduction

Brushes are based on the padding mechanism used to create solid objects and render text objects with the Graphics object.

Introduction of the Path

The definition of the path

The path consists of a set of strictly ordered polylines and curves. The order is important. The path has two rule winding rules. According to the rules, it can be determined whether a point is inside or outside the path (the path is not necessarily closed).

Winding rules

Even-Odd: Rays from one point to the right. If the ray path has an odd number of intersections, the point is in the path; otherwise, the point is no longer in the path.Non-zero rule: ray from one point to the right, if the path from the "up" through the ray does not equal to the number of times from the "down" through the path, then the point is in the path, otherwise, the store No longer in the path.

1 Even-odd rule: points A, D, F are in the path, and points B, C, E, G are not in the path 1 Non-zero rules: Note that the path passes through the direction of the ray, and point A is crossed twice from above, so point A is within the path. Similarly, points D and F are within the path, and points B, C, E, and G are not within the path.

Fill the path with the scan method

The line segment that forms the path can be either a polyline or a curve. In order to facilitate the implementation of the path filling algorithm, it is necessary to dispose the curves as polylines. The following discussion focuses on the implementation of path filling of polylines.

When filling, there may be more than one path, which may be the area formed by multiple paths. Therefore, all paths must maintain the same winding rules, otherwise, they cannot be compared between different paths to determine whether a point is within the path.

Use of path

How to use the path. Paths can be used for path drawing, path filling, and path clipping.Path drawing is to discretize all the sub-path curves in the path into vertices, and then connect all the vertices to draw the path.Path filling is to discretize the path into a polygon and then fill the polygon.Path clipping is similar to path filling, except that the generated scan lines form an area.

Operation on the path: new path, destroyed path, copied path, closed path, adding a straight line to the path, adding a curve to the path, and so on.

Gradient fill

Gradient fill refers to the use of a color linear gradient or a gradual gradient of the brush, in a specified area, or path area, or graphics to fill. With the gradient fill, we can achieve a more beautiful three-dimensional control, which will be detailed in the follow-up. The current gradients implemented by mGPlus are curved gradient fills and linear gradient fills.

Color combination

In the age when product packaging is very important, every application developer wants to develop a very beautiful and refined user interface to get the user's first impression. The color combination is a powerful tool in this area. It can realize the ever-changing combination of pictures and give your interface an unexpected effect. mGPlus implements twelve combination modes.

---+ Architecture

MGPlusGraphics summary

• MiniGUI have two way to use MGPlus：
• First create a memory DC and provide the DC directly to MGPlus, which renders directly on the DC.
• Use MGPlus directly, completely rendered by MGPlus itself, and finally get the rendered DC through the interface function.
• MGPlus internally provides a core data structure MGPlusGraphics , which contains all the data of the graph, including information required for rendering such as paths, gradients, and change matrices. The data structure is not open to the public, only one handle (pointer) is exposed externally.

• Around the `MGPlusGraphics` structure, it will provide a series of

function interfaces to operate, including initialization, parameter

modification, various ways of rendering, and various 2D coordinate changes (such as linear changes).MGPlus includes the following modules:

• MGPlus include follow module:
• pen
• brush
• path
• matrix
• image
• font
• text

• At the bottom, it will be implemented using `AGG` data and

interfaces.

MGPlus Frame Diagram

• MGPlus is mainly composed of the above 9 categories. The Graphic class

implements all operations related to rendering, including color gradient,

color combination, anti-aliasing, etc. The other 8 categories are associated with Graphic in a one-way manner.

• The Matrix class is associated with the Path class, the Image class

and the Bitmap class, and the Font class is associated with the Text

class.

• MGPlus rebuild framework:

---+ API Applications

Graphics

Graphics Manage Functions

The Manage functions of Graphics include the functions of creating, deleting, and copying. Details are as follows:

---++++ Create

There are two ways to create. One is to pass directly into HDC to create MGPlusGraphics Data structure, call function MGPlusGraphicCreateFromDC can successfully return HGRAPHICS, a MGPlusGraphics was created successfully.

Another way is to use a different pixel format to create a MGPlusGraphics data structure, using width and The height is initially used to specify the size of the canvas, calling MGPlusGraphicCreate function. It should be noted that the result of the rendering requires the user to call the interface function MGPlusGraphicSave to obtain it.

Another new way to create. This method creates a MGPlusGraphics for direct drawing DC , Directly incoming DCs operate as canvases.

---++++ Delete

When MGPlusGraphics is not needed, you need to release the MGPlusGraphics data structure by calling The MGPlusGraphicDelete function is fine.

There is another kind of color that can clear MGPlusGraphic, similar to clear screen, this function is MGPlusGraphicClear. Under normal circumstances, when creating MGPlusGraphics, the contents of the relevant dc will also be copied. Therefore, before using MGPlusGraphicCopyFromDC, you need to call this function to clear it. Usage is as follows:

---++++ Copy

Graphics color combination

mGPlus implements some basic alpha Composition rules, combining source color and target color, mixing and transparency effects in graphics and images.

Things to note when implementing:

• Many source images, such as some opaque images, do not store alpha for their pixels value. This type of source image provides an alpha value of 1.0 for all its pixels.

• Many targets also have no place to store alpha Values ​​(these are the results of a hybrid calculation). Such goals implicitly discard such generated alpha value. It is recommended that such objects treat their stored color values ​​as unpremultiplied values, and store the color values ​​and discard them. Before the alpha value, the resulting color value is divided by the resulting alpha value.

• The accuracy of the result depends on how the pixels are stored in the target. For a few of a series of twelve synthesis operations, each color will be The alpha component provides at least 8 The image format of the storage bits should be sufficient as a target anyway. Prior to rounding error dominates the result, less than for each component is provided 8 The image format of the memory bits is limited to one or two synthesis operations. For any translucent mixing type, image formats that do not separately store color components are not a good candidate. For example, you should not need to select pixels from a defined palette to match the mixed equations, so that each operation can introduce a large number of errors.

• Almost all formats store pixels as discrete integers, rather than storing them as floating-point values ​​used in the above equations. The implementation can scale integer pixel values ​​to a range of 0.0 to 1.0 The floating point value between, or using slightly modified equations, operates entirely within the integer domain, producing similar results to the above equation.

• Internal implementations may approximate some equations. They can also eliminate some steps to avoid unnecessary operations.

• Because of techniques that make the calculation more efficient by simplifying the equation, a value of 0.0 is encountered on non-premultiplied targets. The alpha value of the result may be different for some implementation implementations. Note that if the denominator (alpha) Is 0, then divide by alpha under SRC rules This simplified operation is technically illegal. However, because the result is only expected when viewed in premultiplied form, the result is 0 of alpha The value presented is essentially the resulting uncorrelated color component, so in this case, the specific behavior should be unpredictable.

Users need to create two MGPlus Graphics if they need color combinations Finally, they can mix their colors to get the effect of the color combination we want.

The MGPlusGraphics color combination has a total of 12 combination modes, which are:

The user can set the color combination mode according to the need and put the required mode into the function MGPlusSetCompositingMode The parameter compositingMode can be.

If the user wants to get the current color combination mode, directly call the function MGPlusGetCompositingMode to get MGPlusGraphics combination mode. The acquired combination pattern is stored in the address pointed to by compositingMode.

Note: Although the current color combination supports 32-bit color, 24-bit color, 16-bit color, but in 24-bit and 16 In the case of bit depth, only simple color combinations are supported, namely src-over mode.

In addition to the color combinations of graphics, you can also add pictures to participate in color combinations. Users want to add pictures, first call the function MGPlusGraphicLoadBitmapFromFile to load the picture and then call the function MGPlusDrawImage Draw the picture in MGPlusGraphics.

Note: n_index is the prime value of the loaded image; file is the path of the loaded image.

Note: n_index is the prime value of the loaded picture; x, y are the starting position of the picture; w, h is the size of the picture; if w and h are -1, it means that the picture will be drawn with the original size.

There is another way to load pictures. In the initialization of the program calls the function in MiniGUI LoadBitmap (For details, see MiniGUI. API Manual) and then call MGPlusGraphicLoadBitmap and MGPlusDrawImage to draw the picture In MGPlusGraphics, remember to call MiniGUI in the end of the program UnloadBitmap The function frees memory space.

Note: n_index is the prime value of the loaded image; p_bitmap is the address of the stored image.

After completing the corresponding work, be sure to call the function MGPlusGraphicBlend, otherwise the effect of the color combination is invisible.

For details on how to combine colors, see the example of color combinations:

color combination

Graphics mode

Graphics rendering mode is anti-aliasing control, including brush smooth mode, path anti-aliasing and text anti-aliasing.

---++++ Brush's smooth mode

There are two kinds of smooth brush modes, which are:

The user wants to set the drawing mode of the brush. The MGPlusSetSmoothingMode function can be used as the following example:

To get the drawing mode of the current brush, call the MGPlusGetSmoothingMode function, The value of the drawing mode is stored in the address of the value.

---++++ Path antialiasing

Path anti-aliasing controls anti-aliasing with MP_PATH_RENDER_HINT_ANTIALIAS_ON and MP_PATH_RENDER_HINT_ANTIALIAS_OFF.

Users want to set the path anti-aliasing drawing mode, use MGPlusSetPathRenderingHint function, the specific usage is as follows:

To get the current path anti-aliased drawing mode, call MGPlusGetPathRenderingHint function, The value of the drawing mode is stored in the address of the value.

Add the effect of the path before anti-aliasing

Adding the anti-aliasing effect of the path

Added anti-aliasing effect of the path

Adding anti-aliasing effect to the path

---++++ Text Antialiasing

Anti-aliasing of text is controlled by MP_TEXT_RENDER_HINT_ANTIALIAS_ON and MP_TEXT_RENDER_HINT_ANTIALIAS_OFF.

Users want to set the text anti-aliasing drawing mode, you can use MGPlusSetTextRenderingHint function, the specific usage of the following example:

To get the current text anti-aliasing drawing mode, call the function MGPlusGetTextRenderingHint, The value of the drawing mode is stored in the address of the value.

Add text before antialiasing

Add text anti-aliasing effect

Added text anti-aliasing effect

Add text anti-aliasing effect

World Coordinate System Conversion

The conversion of the world coordinate system is the conversion (translation, scaling, rotation) of the coordinates of MGPlus Graphics. There is also a path conversion of mgplus, which is the conversion of the coordinates of the graphics coordinates (translation, scaling, rotation).

---++++ Settings

The user needs to set the world coordinate system to call the MGPlusSetWorldTransform function.

The definition of the parameter matrix is ​​as follows:

Reset the function to MGPlusResetWorldTransform.

---++++ Translation

If the user wants to translate, it should be noted that: the first world coordinate is (0, 0), if you want to figure around (100, 100) Rotate the coordinates first to (100, 100), ie using MGPlusTranslateWorldTransform(graphics,-100, -100), then use Rotatate rotation, and finally use MGPlusTranslateWorldTransform(graphics, 100, 100), translate coordinates back.

---++++ Zoom

Call the function MGPlusScaleWorldTransform , users can zoom MGPlusGraphics.

---++++ Rotation

The function MGPlusRotateWorldTransform is called and the user can rotate the MGPlus Graphics.

The specific usage can refer to the following example of the conversion of the world coordinate system:

Conversion of world coordinate system

View Description: The bottom layer is the original graphics, the upper layer is twice the x-axis magnification, and the rotated 70-degree conversion graphics.

Font Rendering

Currently, mgplus only supports rendering of vector fonts, so if you need font rendering functionality, you first need to open it when compiling mgplus --enable-ft2support The option is used to support freetype2 vector fonts, and requires the client to add freetype libraries when compiling the application.

Users want to draw fonts, first create a font using the MGPlusCreateFont function.

There are six modes for font rendering, as follows:

After the font is created, the outline data of the font is obtained by the function MGPlusGetGlyphOutline.

The parameter lpdata is the data for storing the font outline.

The function of LPGLYPHMETRICS The lpgm parameter includes the position, direction and size of the font outline. The specific definition is as follows:

Then the font can be drawn according to the outline data of the font, or the path structure of the font can be used to rotate the font. The functions used are as follows:

Note: x, y refer to the starting coordinates of the drawing font; lpdata is the data for storing the font outline; color refers to the drawing color of the font.

Note: x, y refer to the starting coordinates of the drawing font.

Finally, after the corresponding operation is completed, the font is deleted to avoid memory leaks. The function is MGPlusDeleteFont.

The font rotation sample code is as follows:

font rotation

Path

Path Management

Path: A path consists of a set of strictly ordered polylines and curves. Paths can be used for filling and cutting. By providing support for the path, we can achieve drawing of vector graphics, support for vector graphics, such as infinity zooming and rotation, as well as providing better support for vector fonts.

---++++ Create

When MGPlusPathCreate creates a path, you need to select the winding rule. The winding rule is divided into two types:

• MP_PATH_FILL_MODE_WINDING // Non-zero rule
• MP_PATH_FILL_MODE_ALTERNATE // odd and even rules

E.g:

---++++ Delete

Release path. If you do not release the memory in the application, it will lead to memory leaks and coredump.

---++++ Reset

Reset the path. Clear all the contents of the path.

---++++ fill path

MGPlusFillPath Before filling the path, you must determine the Brush fill feature and then use MGPlusGraphicSave to draw to the screen.

The specific application is explained in detail in the next section "Adding a graphic to a path".

---++++ Add graphics to the path ---+++++ Add Line

Pass the coordinates of the two points to draw a straight line.

Pass in a group of "points" and draw straight lines in order of the points. Count is the number of vertices.

E.g:

Drawing Effective Results

---+++++ Add an arc

(cx, cy) is the center point coordinate of the ellipse, rx is the radius of the X axis, ry For the y-axis radius, startangle is the arc start angle, and sweepAngle is the radians between the start and end angles.

E.g:

---+++++ Add Bezier Curve

(x1,y1) is the starting point, (x2,y2) is the first control point, (x3, Y3) is the second control point, and (x4, y4) is the end point.

E.g:

---+++++ Add a rectangle

(x, y) is the vertices of the rectangle, and (width, height) is the length and width of the rectangle.

E.g:

---+++++ Add Rounded Rectangle

(x, y) is a rectangle vertex, (width, Height) is the length and width of the rectangle. The rounded rectangle of the rounded rectangle is calculated by a rectangle, and the size of the rectangle is used ( Rx, ry) to control.

E.g:

---+++++ Add ellipse

(cx, cy) is an ellipse center, (rx, ry) is an elliptical x-radius, y-radius, clockwise In the drawing direction of the ellipse, TRUE is clockwise and FALSE is counterclockwise.

E.g:

---+++++ Add curves

Points Vertex array, count Number of vertices.

E.g:

---+++++ Add path

Add the contents of add_path to path.

E.g:

---++++ Drawing path

MGPlusDrawPath To draw the path, you must determine the Pen drawing properties and then use MGPlusGraphicSave to draw to the screen.

MGPlusDrawPath is similar to MGPlusFillPath.

E.g:

---++++ Open and close

Start a new subpath in the path. Subpaths allow you to divide a path into sections and use it.

Closed path. Once the subpath is closed, the next line drawn in the path starts from another path.

E.g:

---++++ Line Control

Move the current pen to another point without drawing a line.

Use the current pen's point as a starting point to draw another line.

E.g:

---++++ Get path

E.g:

path conversion

mGPlus provides matrix objects, a very powerful tool that makes it very easy to write rotations, translations, and scales for graphics. A matrix object is always associated with a graphic transformation pair. For example, the PATH has a Transform method. One of its parameters can accept the address of the matrix object. Each time the path is drawn, it can be based on the transformation matrix. draw. The graphics transformation is stored in the transformation matrix, so the path transformation is the transformation of the graph. Path conversion matrices can be set, and translations, scaling, and rotations can also be applied to the path.

---++++ Settings

Call the MGPlusPathSetTransform function to set the transformation matrix for the path.

The definition of the parameter matrix is as follows:

Call the MGPlusPathResetTransform function to reset the conversion matrix for the path.

---++++ Translation

Calling the MGPlusPathTranslate function, the path is translated from the original position along the x and y axes (dx, dy).

---++++ Zoom

The function MGPlusPathScale is used to scale the path. The value of sx , sy is greater than 1 is magnified, less than 1 is reduced.

---++++ Rotation

The function MGPlusPathRotate is used for the rotation of the path, and the parameter angle is the rotation angle value.

Note: After the matrix is converted as required, the MGPlusPathTransform function must be called. This function applies the matrix transformation; otherwise, the effect of path conversion cannot be displayed.

For the usage of path conversion, please refer to the following example:

path conversion

Pen

Pen Management

Brushes are used to draw lines, curves, and outlines of shapes. They are based on point-painting mechanisms. In addition to the common color and width attributes, the pen also has properties such as alignment, caps, and transitions.

---++++ Create Pen

If the user wants to use the pen to draw the shape, he needs to call the function MGPlusPenCreate to create the pen. %CODE{cpp}% HPEN MGPlusPenCreate (int width, ARGB argb);

Pen Settings

After the pen is created, the user needs to set the pen as needed, such as the color, width, connection, and length of the dotted line.

---++++ Color Settings

If the user needs to modify the color of the pen, call the function MGPlusPenSetColor.

---++++ width setting

If the user needs to modify the width of the pen, call the function MGPlusPenSetWidth.

Width rendering

Effect of width Note: The width of the lines is 1, 10 and 30 in order.

---++++ Dashed length setting

The pen is drawn in the default state is a solid line, the user wants to set the dotted line, call the function MGPlusPenSetDashes To set, use the parameter dash_list to use a predefined array to describe the virtual reality of the pen . The dotted style depends on an array, The elements of the array represent the lengths of the dashed lines and spaces, respectively.

Note: The parameter dash_phase is, dash_list is the dotted line shape, dash_len is the length of the dotted line shape. Dotted effect chart

Drawing effect chart Explanation: The style of the dotted line is {5, 10, 20}, {5, 10, 20, 15} and {5, 10, 20, 15, 10,}.

---++++ Connection settings

The connection mode refers to the setting of the shape of the connection when two straight lines are connected. There are five ways: JOIN_MITER (mock), JOIN_ROUND (round), JOIN_BEVEL (diagonal) JOIN_MILTER_REVERT, JOIN_MILTER_ROUND. The function MGPlusPenSetJoinStyle is called to modify the shape of the two straight line connections.

Set the mode to the effect of JOIN_MITER

mode is JOIN_MITER

The set mode is JOIN_ROUND

mode is JOIN_ROUND

Set the pattern to the effect of JOIN_BEVEL

mode is JOIN_BEVEL

The user wants to modify the shape of the head and tail of the drawn line by calling MGPlusPenSetCapStyle function. There are three ways: CAP_BUTT (flat cap) CAP_ROUND (round line cap), CAP_SQUARE (square line cap).

Set the mode to CAP_BUTT renderings

mode is CAP_BUTT

Set the mode to CAP_ROUND renderings

mode is CAP_ROUND

Effect mode for setting the mode to CAP_SQUARE

mode is CAP_SQUARE

An example of a connection method is as follows:

Description: If you are running MGPlusPenSetCapStyle effect, open the masked, then close the relevant point of JoinStyle.

Drawing graphics

The MGPlusFillPath and MGPlusGraphicSave procedures are not required, and the image can be drawn directly with the pen.

---++++ Draw a straight line

Two points drawn in a straight line

E.g:

---++++ Drawing Arcs

(cx, cy) is the center point coordinate of the ellipse, rx is the radius of the X axis, ry For the y-axis radius, startangle is the arc start angle, and sweepAngle is the radians between the start and end angles.

E.g:

---++++ Drawing Bezier Curves

(x1,y1) is the starting point, (x2,y2) is the first control point, (x3, Y3) is the second control point, and (x4, y4) is the end point.

E.g:

---++++ draw a rectangle

(x, y) is the vertices of the rectangle, and (width, height) is the length and width of the rectangle.

E.g:

---++++ Drawing Rounded Rectangle

(x, y) is a rectangle vertex, (width, Height) is the length and width of the rectangle. The rounded rectangle of the rounded rectangle is calculated by a rectangle, and the size of the rectangle is used ( Rx, ry) to control.

E.g:

---++++ Draw an ellipse

(cx, cy) is an ellipse center, (rx, ry) is an elliptical x-radius, y-radius

E.g:

---++++ Load image

The bitmap used by mgplus must be format compatible with graphics, so from other dc-loaded bitmaps, you need to convert. Two ways to load pictures:

---++++ Drawing pictures

There are three ways to draw a picture:

E.g:

E.g:

E.g:

Brush

Brush Management

The brush is based on a padding mechanism that is used with the Graphics object to create a solid shape and an object that renders text.

---++++ Create

Select brush style when using MGPlusBrushCreate to create a brush %CODE{cpp}% Typedef enum _MPBrushType { /* Brush the path with the single color./ MP_BRUSH_TYPE_SOLIDCOLOR = 0, / Brush the path with the hatchfill./ MP_BRUSH_TYPE_HATCHFILL = 1, / Brush the path with the texturefill./ MP_BRUSH_TYPE_TEXTUREFILL = 2, / Brush the path with the path gradient./ MP_BRUSH_TYPE_PATHGRADIENT = 3, / Brush the path with linear gradient.*/ MP_BRUSH_TYPE_LINEARGRADIENT }MPBrushType;

HBRUSH MGPlusBrushCreate (MGPlusBrushType type);

Brush Settings

---++++ Solid Brush Setting

Set the color of a single brush

---++++ `GradientBrush` `GradientBrush` Settings

---+++++ Path Gradient Brush PathGradientBrush Settings

Set the center point of PathGradientBrush

Set the color of the center of the PathGradientBrush

Set the PathGradientBrush wrapping color

Set the scope of the arc gradient of the PathGradientBrush

E.g:

---+++++ Linear GradientBrush LinearGradientBrus Settings

Set the LinearGradientBrush mode

Get LinearGradientBrush mode

Set the LinearGradientBrush area

Set the LinearGradientBrush gradient color

E.g:

MP_LINEAR_GRADIENT_MODE_HORIZONTAL. The following is a demonstration of other modes: Set brush to `MP_LINEAR_GRADIENT_MODE_VERTICAL` mode

MP_LINEAR_GRADIENT_MODE_VERTICAL

Set brush to MP_LINEAR_GRADIENT_MODE_FORWARDDIAGONAL mode

MP_LINEAR_GRADIENT_MODE_FORWARDDIAGONAL

Set the brush to MP_LINEAR_GRADIENT_MODE_BACKWARDDIAGONAL mode

MP_LINEAR_GRADIENT_MODE_BACKWARDDIAGONAL

Fill graphic

There is no need for the MGPlusFillPath and MGPlusGraphicSave procedures to fill the image directly with the paintbrush.

---++++ Fill the arc

(cx, cy) is the center point coordinate of the ellipse, rx is the radius of the X axis, ry For the y-axis radius, startangle is the arc start angle, and sweepAngle is the radians between the start and end angles.

E.g:

---++++ Fill Bezier Curve

(x1,y1) is the starting point, (x2,y2) is the first control point, (x3, Y3) is the second control point, and (x4, y4) is the end point.

E.g:

---++++ Fill rectangle

(x, y) is the vertices of the rectangle, and (width, height) is the length and width of the rectangle.

E.g:

---++++ Fill rounded rectangle

(x, y) is a rectangle vertex, (width, Height) is the length and width of the rectangle. The rounded rectangle of the rounded rectangle is calculated by a rectangle, and the size of the rectangle is used ( Rx, ry) to control.

E.g:

---++++ Fill ellipse

(cx, cy) is an ellipse center, (rx, ry) is an elliptical x-radius, y-radius

E.g:

---

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