iOS Development UI Chapter-quartz2d use (Matrix operations)

iOS Development UI Chapter-quartz2d use (Matrix operations)

first, about the matrix operation 1. Draw a quadrilateralA four-sided drawing is done by setting two endpoints (length and width). Code:

-(void) DrawRect: (cgrect) rect{    // draw quadrilateral     // Get Graphics context    cgcontextref ctx=uigraphicsgetcurrentcontext ();     // Drawing    Cgcontextaddrect (CTX, CGRectMake ());     // Rendering     Cgcontextstrokepath (CTX);}

Description:There are weaknesses in drawing rectangles in this way:The drawn rectangle is always positive. such as:

2. Draw a crooked quadrilateralHow to draw a crooked rectangle? (Done with a matrix operation, similar to a deformation operation) can be manipulated by the matrix to deform (rotate, scale, pan) the object of the drawing (rotation, scaling, panning) method:CGCONTEXTROTATECTM (< #CGContextRef C#>, < #CGFloat angle#>) This accepts two parameters (graphics context, radians)watch out.:Setting the matrix operation must be done before adding the graphic, if it is finished after adding the graphic, it is not valid at this time. Code:

- (void) DrawRect: (cgrect) rect{//Draw Quadrilateral//Get the graphics contextCgcontextref ctx=Uigraphicsgetcurrentcontext (); //Matrix Operations//Note: The set matrix operation must be preceded by the addition of the drawing information.//Rotate 45 degreesCGCONTEXTROTATECTM (CTX, m_pi_4); //DrawingCgcontextaddrect (CTX, CGRectMake ( Max, -, -, -)); //RenderingCgcontextstrokepath (CTX);}

Effect:

Ii. about rotation 1. Rotate the demo view to display the view because it has a layer above it and the future graph is rendered to the layer. And, when rotating the entire layer is rotated, you can draw a circle to verify. Code 1 (not rotated):

- (void) DrawRect: (cgrect) rect{//Get the graphics contextCgcontextref ctx=Uigraphicsgetcurrentcontext (); //Matrix Operations//Note: The set matrix operation must be preceded by the addition of the drawing information.//Rotate 45 degrees//CGCONTEXTROTATECTM (CTX, m_pi_4); //Drawing//Draw QuadrilateralCgcontextaddrect (CTX, CGRectMake ( Max, -, -, -)); //Draw a circleCgcontextaddellipseinrect (CTX, CGRectMake ( $, $, -, -)); //RenderingCgcontextstrokepath (CTX);}

Effect:

Code 2 (rotation):

- (void) DrawRect: (cgrect) rect{//Get the graphics contextCgcontextref ctx=Uigraphicsgetcurrentcontext (); //Matrix Operations//Note: The set matrix operation must be preceded by the addition of the drawing information.//Rotate 45 degreesCGCONTEXTROTATECTM (CTX, m_pi_4); //Drawing//Draw QuadrilateralCgcontextaddrect (CTX, CGRectMake ( Max, -, -, -)); //Draw a circleCgcontextaddellipseinrect (CTX, CGRectMake ( $, $, -, -)); //RenderingCgcontextstrokepath (CTX);}

Effect:

2. Additional Notes on rotationTips:When rotated, the entire layer is rotated. Three, the scaling method:CGCONTEXTSCALECTM (< #CGContextRef C#>, < #CGFloat Sx#>, < #CGFloat sy#>)The method receives three parameters (the graph context, the X-direction scale, and the scaling code example in the y direction):

- (void) DrawRect: (cgrect) rect{//Get the graphics contextCgcontextref ctx=Uigraphicsgetcurrentcontext (); //Matrix Operations//Note: The set matrix operation must be preceded by the addition of the drawing information.//Scaling , X-direction scaling 0.5 times times, y-direction scaling 1.5 times timesCGCONTEXTSCALECTM (CTX,0.5,1.5); //Drawing//Draw QuadrilateralCgcontextaddrect (CTX, CGRectMake ( Max, -, -, -)); //Draw a circleCgcontextaddellipseinrect (CTX, CGRectMake ( $, $, -, -)); //RenderingCgcontextstrokepath (CTX);}

Effect:

Four, the translation method:CGCONTEXTTRANSLATECTM (< #CGContextRef C#>, < #CGFloat Tx#>, < #CGFloat ty#>)The method receives three parameters (graph context, offset in x direction, offset in y direction) code example:

- (void) DrawRect: (cgrect) rect{//Get the graphics contextCgcontextref ctx=Uigraphicsgetcurrentcontext (); //Matrix Operations//Note: The set matrix operation must be preceded by the addition of the drawing information.//Shift , X-direction move 50,y directionCGCONTEXTTRANSLATECTM (CTX, -, -); //Drawing//Draw QuadrilateralCgcontextaddrect (CTX, CGRectMake ( Max, -, -, -)); //Draw a circleCgcontextaddellipseinrect (CTX, CGRectMake ( $, $, -, -)); //RenderingCgcontextstrokepath (CTX);}

Effect:

Tip: The coordinate origin is the upper-left corner of the view.

iOS Development UI Chapter-quartz2d use (Matrix operations)