CGContext
Quartz 2D绘图环境。
定义
class CGContext
CGContext类型表示Quartz 2D绘图目标。图形上下文包含绘图参数和将页面上的绘画渲染到目标所需的所有特定于设备的信息，无论目标是应用程序中的窗口，位图图像，PDF文档还是打印机。
主题
创建位图图形上下文
init?(data: UnsafeMutableRawPointer?, width: Int, height: Int, bitsPerComponent: Int, bytesPerRow: Int, space: CGColorSpace, bitmapInfo: UInt32) Creates a bitmap graphics context.
init?(data: UnsafeMutableRawPointer?, width: Int, height: Int, bitsPerComponent: Int, bytesPerRow: Int, space: CGColorSpace, bitmapInfo: UInt32, releaseCallback: CGBitmapContextReleaseDataCallback?, releaseInfo: UnsafeMutableRawPointer?) Creates a bitmap graphics context with the specified callback function.
typealias CGBitmapContextReleaseDataCallback A callback function used to release data associate with the bitmap context.
创建PDF图形上下文
init?(CFURL, mediaBox: UnsafePointer
init?(consumer: CGDataConsumer, mediaBox: UnsafePointer
Auxiliary Dictionary Keys Keys for the auxiliary info dictionary you specify when creating a PDF context.
在坐标空间之间转换
var userSpaceToDeviceSpaceTransform: CGAffineTransform Returns an affine transform that maps user space coordinates to device space coordinates.
func convertToDeviceSpace(CGPoint) -> CGPoint Returns a point that is transformed from user space coordinates to device space coordinates.
func convertToUserSpace(CGPoint) -> CGPoint Returns a point that is transformed from device space coordinates to user space coordinates.
func convertToDeviceSpace(CGRect) -> CGRect Returns a rectangle that is transformed from user space coordinate to device space coordinates.
func convertToUserSpace(CGRect) -> CGRect Returns a rectangle that is transformed from device space coordinate to user space coordinates.
func convertToDeviceSpace(CGSize) -> CGSize Returns a size that is transformed from user space coordinates to device space coordinates.
func convertToUserSpace(CGSize) -> CGSize Returns a size that is transformed from device space coordinates to user space coordinates.
构造当前图形路径
func beginPath() Creates a new empty path in a graphics context.
func move(to: CGPoint) Begins a new subpath at the specified point.
func addLine(to: CGPoint) Appends a straight line segment from the current point to the specified point.
func addLines(between: [CGPoint]) Adds a sequence of connected straight-line segments to the current path.
func addRect(CGRect) Adds a rectangular path to the current path.
func addRects([CGRect]) Adds a set of rectangular paths to the current path.
func addEllipse(in: CGRect) Adds an ellipse that fits inside the specified rectangle.
func addArc(center: CGPoint, radius: CGFloat, startAngle: CGFloat, endAngle: CGFloat, clockwise: Bool) Adds an arc of a circle to the current path, specified with a radius and angles.
func addArc(tangent1End: CGPoint, tangent2End: CGPoint, radius: CGFloat) Adds an arc of a circle to the current path, specified with a radius and two tangent lines.
func addCurve(to: CGPoint, control1: CGPoint, control2: CGPoint) Adds a cubic Bézier curve to the current path, with the specified end point and control points.
func addQuadCurve(to: CGPoint, control: CGPoint) Adds a quadratic Bézier curve to the current path, with the specified end point and control point.
func addPath(CGPath) Adds a previously created path object to the current path in a graphics context.
func closePath() Closes and terminates the current path’s subpath.
var path: CGPath? Returns a path object built from the current path information in a graphics context.
func replacePathWithStrokedPath() Replaces the path in the graphics context with the stroked version of the path.
检查当前图形路径
var boundingBoxOfPath: CGRect Returns the smallest rectangle that contains the current path.
var currentPointOfPath: CGPoint Returns the current point in a non-empty path.
var isPathEmpty: Bool Indicates whether the current path contains any subpaths.
func pathContains(CGPoint, mode: CGPathDrawingMode) -> Bool Checks to see whether the specified point is contained in the current path.
绘制当前图形路径
func drawPath(using: CGPathDrawingMode) Draws the current path using the provided drawing mode.
enum CGPathDrawingMode Options for rendering a path.
func fillPath(using: CGPathFillRule) Paints the area within the current path, as determined by the specified fill rule.
func strokePath() Paints a line along the current path.
绘制形状
func clear(CGRect) Paints a transparent rectangle.
func fill(CGRect) Paints the area contained within the provided rectangle, using the fill color in the current graphics state.
func fill([CGRect]) Paints the areas contained within the provided rectangles, using the fill color in the current graphics state.
func fillEllipse(in: CGRect) Paints the area of the ellipse that fits inside the provided rectangle, using the fill color in the current graphics state.
func stroke(CGRect) Paints a rectangular path.
func stroke(CGRect, width: CGFloat) Paints a rectangular path, using the specified line width.
func strokeEllipse(in: CGRect) Strokes an ellipse that fits inside the specified rectangle.
func strokeLineSegments(between: [CGPoint]) Strokes a sequence of line segments.
绘制图像和PDF内容
func draw(CGImage, in: CGRect, byTiling: Bool) Draws an image in the specified area.
func drawPDFPage(CGPDFPage) Draws the content of a PDF page into the current graphics context.
var interpolationQuality: CGInterpolationQuality Returns the current level of interpolation quality for a graphics context.
enum CGInterpolationQuality Levels of interpolation quality for rendering an image.
绘制渐变和底纹
func drawLinearGradient(CGGradient, start: CGPoint, end: CGPoint, options: CGGradientDrawingOptions) Paints a gradient fill that varies along the line defined by the provided starting and ending points.
func drawRadialGradient(CGGradient, startCenter: CGPoint, startRadius: CGFloat, endCenter: CGPoint, endRadius: CGFloat, options: CGGradientDrawingOptions) Paints a gradient fill that varies along the area defined by the provided starting and ending circles.
struct CGGradientDrawingOptions Drawing locations for gradients.
func drawShading(CGShading) Fills the clipping path of a context with the specified shading.
绘制文字
var textMatrix: CGAffineTransform Returns the current text matrix.
var textPosition: CGPoint Returns the location at which text is drawn.
func setCharacterSpacing(CGFloat) Sets the current character spacing.
func setFont(CGFont) Sets the platform font in a graphics context.
func setFontSize(CGFloat) Sets the current font size.
func setTextDrawingMode(CGTextDrawingMode) Sets the current text drawing mode.
enum CGTextDrawingMode Modes for rendering text.
func setAllowsFontSmoothing(Bool) Sets whether or not to allow font smoothing for a graphics context.
func setAllowsFontSubpixelPositioning(Bool) Sets whether or not to allow subpixel positioning for a graphics context.
func setAllowsFontSubpixelQuantization(Bool) Sets whether or not to allow subpixel quantization for a graphics context.
func setShouldSmoothFonts(Bool) Enables or disables font smoothing in a graphics context.
func setShouldSubpixelPositionFonts(Bool) Enables or disables subpixel positioning in a graphics context.
func setShouldSubpixelQuantizeFonts(Bool) Enables or disables subpixel quantization in a graphics context.
func showGlyphs([CGGlyph], at: [CGPoint]) Draws a set of glyphs at a set of corresponding positions.
绘制核心图形层
func draw(CGLayer, at: CGPoint) Draws the contents of a layer object at the specified point.
func draw(CGLayer, in: CGRect) Draws the contents of a layer object into the specified rectangle.
设置填充，描边和阴影颜色
func setFillColor(CGColor) Sets the current fill color in a graphics context, using a CGColor.
func setFillColor(UnsafePointer
func setFillColor(cyan: CGFloat, magenta: CGFloat, yellow: CGFloat, black: CGFloat, alpha: CGFloat) Sets the current fill color to a value in the DeviceCMYK color space.
func setFillColor(gray: CGFloat, alpha: CGFloat) Sets the current fill color to a value in the DeviceGray color space.
func setFillColor(red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) Sets the current fill color to a value in the DeviceRGB color space.
func setFillColorSpace(CGColorSpace) Sets the fill color space in a graphics context.
func setShadow(offset: CGSize, blur: CGFloat) Enables shadowing in a graphics context.
func setShadow(offset: CGSize, blur: CGFloat, color: CGColor?) Enables shadowing with color a graphics context.
func setStrokeColor(CGColor) Sets the current stroke color in a context, using a CGColor.
func setStrokeColor(UnsafePointer
func setStrokeColor(cyan: CGFloat, magenta: CGFloat, yellow: CGFloat, black: CGFloat, alpha: CGFloat) Sets the current stroke color to a value in the DeviceCMYK color space.
func setStrokeColor(gray: CGFloat, alpha: CGFloat) Sets the current stroke color to a value in the DeviceGray color space.
func setStrokeColor(red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) Sets the current stroke color to a value in the DeviceRGB color space.
func setStrokeColorSpace(CGColorSpace) Sets the stroke color space in a graphics context.
func setStrokePattern(CGPattern, colorComponents: UnsafePointer
func setAlpha(CGFloat) Sets the opacity level for objects drawn in a graphics context.
使用当前的剪切路径
func clip(using: CGPathFillRule) Modifies the current clipping path.
func clip(to: CGRect) Sets the clipping path to the intersection of the current clipping path with the area defined by the specified rectangle.
func clip(to: [CGRect]) Sets the clipping path to the intersection of the current clipping path with the region defined by an array of rectangles.
func clip(to: CGRect, mask: CGImage) Maps a mask into the specified rectangle and intersects it with the current clipping area of the graphics context.
var boundingBoxOfClipPath: CGRect Returns the bounding box of a clipping path.
使用透明层
func beginTransparencyLayer(in: CGRect, auxiliaryInfo: CFDictionary?) Begins a transparency layer whose contents are bounded by the specified rectangle.
func beginTransparencyLayer(auxiliaryInfo: CFDictionary?) Begins a transparency layer.
func endTransparencyLayer() Ends a transparency layer.
使用当前转换矩阵
var ctm: CGAffineTransform Returns the current transformation matrix.
func rotate(by: CGFloat) Rotates the user coordinate system in a context.
func scaleBy(x: CGFloat, y: CGFloat) Changes the scale of the user coordinate system in a context.
func translateBy(x: CGFloat, y: CGFloat) Changes the origin of the user coordinate system in a context.
func concatenate(CGAffineTransform) Transforms the user coordinate system in a context using a specified matrix.
设置路径绘制选项
func setAllowsAntialiasing(Bool) Sets whether or not to allow antialiasing for a graphics context.
func setFlatness(CGFloat) Sets the accuracy of curved paths in a graphics context.
func setLineCap(CGLineCap) Sets the style for the endpoints of lines drawn in a graphics context.
func setLineDash(phase: CGFloat, lengths: [CGFloat]) Sets the pattern for drawing dashed lines.
func setLineJoin(CGLineJoin) Sets the style for the joins of connected lines in a graphics context.
func setLineWidth(CGFloat) Sets the line width for a graphics context.
func setMiterLimit(CGFloat) Sets the miter limit for the joins of connected lines in a graphics context.
func setPatternPhase(CGSize) Sets the pattern phase of a context.
func setFillPattern(CGPattern, colorComponents: UnsafePointer
func setShouldAntialias(Bool) Sets antialiasing on or off for a graphics context.
保存和还原图形状态
func saveGState() Pushes a copy of the current graphics state onto the graphics state stack for the context.
func restoreGState() Sets the current graphics state to the state most recently saved.
管理图形上下文
func flush() Forces all pending drawing operations in a window context to be rendered immediately to the destination device.
func synchronize() Marks a window context for update.
func setBlendMode(CGBlendMode) Sets how sample values are composited by a graphics context.
enum CGBlendMode Compositing operations for images.
func setRenderingIntent(CGColorRenderingIntent) Sets the rendering intent in the current graphics state.
管理位图图形上下文
These properties and methods are valid only when used with a CGContext object created with the initializers listed in Creating Bitmap Graphics Contexts.Creating Bitmap Graphics Contexts
var bitmapInfo: CGBitmapInfo Obtains the bitmap information associated with a bitmap graphics context.
var alphaInfo: CGImageAlphaInfo Returns the alpha information associated with the context, which indicates how a bitmap context handles the alpha component.
var bitsPerComponent: Int Returns the bits per component of a bitmap context.
var bitsPerPixel: Int Returns the bits per pixel of a bitmap context.
var bytesPerRow: Int Returns the bytes per row of a bitmap context.
var colorSpace: CGColorSpace? Returns the color space of a bitmap context.
var data: UnsafeMutableRawPointer? Returns a pointer to the image data associated with a bitmap context.
var height: Int Returns the height in pixels of a bitmap context.
var width: Int Returns the width in pixels of a bitmap context.
func makeImage() -> CGImage? Creates and returns a CGImage from the pixel data in a bitmap graphics context.
管理PDF图形上下文
These methods are valid only when used with a CGContext object created with the initializers listed in Creating PDF Graphics Contexts.
func beginPDFPage(CFDictionary?) Begins a new page in a PDF graphics context.
func endPDFPage() Ends the current page in the PDF graphics context.
func addDestination(CFString, at: CGPoint) Sets a destination to jump to when a point in the current page of a PDF graphics context is clicked.
func setDestination(CFString, for: CGRect) Sets a destination to jump to when a rectangle in the current PDF page is clicked.
func setURL(CFURL, for: CGRect) Sets the URL associated with a rectangle in a PDF graphics context.
func addDocumentMetadata(CFData?) Associates custom metadata with the PDF document.
func closePDF() Closes a PDF document.
管理基于页面的图形上下文
func beginPage(mediaBox: UnsafePointer
func endPage() Ends the current page in a page-based graphics context.
使用核心基础类型
class var typeID: CFTypeID Returns the type identifier for a graphics context.
常量
enum CGPathFillRule Rules for determining which regions are interior to a path, used by the fillPath(using:) and clip(using:) methods.
实例方法
func resetClip()
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