class

PNGGIF::Painter

Inherits Reference < Object

A small QPainter-style 2D rasterizer that draws into a PNGGIF::Bitmap (RGBA pixels). Backend-agnostic: knows nothing about terminals, cells, braille or sixel. Extracted from Crysterm, where Graph::Canvas allocates the bitmap at the native resolution of whatever Media backend the terminal supports and hands it here; the same paint code renders identically to braille, sixel, kitty, …

Coordinates are logical. #set_window (logical bounds) and #set_viewport (device-pixel bounds) define an affine logical→device map, like QPainter#setWindow/#setViewport: declare your data space once and draw resolution-independently. With no window set, logical units equal device pixels.

#pen is the stroke color (0xRRGGBB); #pen_alpha its opacity. X and Y scale independently (so axis-aligned plots fill the viewport regardless of the device's pixel aspect); #draw_ellipse additionally honors #pixel_aspect so circles stay round on non-square backends.

Constants

ELLIPSE_R_MAX = 20000

Device-radius cap for #ellipse: keeps the midpoint algorithm's squared terms within Int64 and its iteration count bounded on pathological radii.

PX_LIMIT = 1000000

Off-canvas magnitude for device coordinates. Non-finite or out-of-range logical inputs map here — well outside any real bitmap, so #plot's bounds check rejects them — while staying far enough from Int32's limits that downstream pixel arithmetic (marker/ellipse offsets, Bresenham deltas) can't itself overflow.

Constructors

new(bmp : PNGGIF::Bitmap)
Source

Instance methods

clear(color : Int32 = 0, alpha : UInt8 = 0_u8) : Nil

Fills the whole bitmap with color (default fully transparent, since translucent pixels leave the terminal untouched).

Source
draw_ellipse(cx : Number, cy : Number, rx : Number, ry : Number) : Nil

Draws an axis-aligned ellipse outline centered at logical (cx, cy) with logical radii (rx, ry). Radii map to device space; #pixel_aspect corrects the vertical radius so an intended circle stays round on non-square backends.

Source
draw_line(x0 : Number, y0 : Number, x1 : Number, y1 : Number) : Nil
Source
draw_marker(x : Number, y : Number, radius : Int32 = 1) : Nil

Draws a small filled square marker (radius in device pixels) centered on the logical point — a single pixel is too faint for scatter points.

Source
draw_point(x : Number, y : Number) : Nil
Source
draw_polyline(points : Array(Tuple(Float64, Float64))) : Nil

Connects consecutive points with line segments.

Source
draw_rect(x : Number, y : Number, w : Number, h : Number) : Nil

Outlines a rectangle (logical x,y = top-left; w,h = size).

Source
fill_rect(x : Number, y : Number, w : Number, h : Number) : Nil

Fills a rectangle solid.

Source
fill_ring(cx : Number, cy : Number, r_inner : Number, r_outer : Number, start_deg : Number = 0.0, sweep_deg : Number = 360.0, step_deg : Number = 0.7) : Nil

Fills an annular sector (ring arc) in device pixels, centered at device (cx, cy), between r_inner..r_outer radii, over start_deg.. start_deg + sweep_deg. 0° is up (12 o'clock), angles increase clockwise. Vertical radius is scaled by #pixel_aspect so the ring is physically round on non-square backends. Works in device space, so the geometry is independent of any window/viewport.

Source
height
Source
pen=(v : Int32) : Int32

Sets the stroke color, and recomputes @pen_px so the RGB unpack happens once per stroke instead of once per plotted pixel.

Source
pen_alpha
Source
pen_alpha=(v : UInt8) : UInt8

Sets the stroke opacity, and recomputes the blend-invariant @pen_af/@pen_ia factors so #plot doesn't redo the /255.0 division per pixel.

Source
pixel_aspect

Physical width:height of one device pixel (1.0 = square). Used by #draw_ellipse so an intended circle isn't squashed on backends whose device pixels aren't square (block/quadrant/sextant).

Source
pixel_aspect=(pixel_aspect : Float64)

Physical width:height of one device pixel (1.0 = square). Used by #draw_ellipse so an intended circle isn't squashed on backends whose device pixels aren't square (block/quadrant/sextant).

Source
set_viewport(x : Number, y : Number, w : Number, h : Number) : Nil

Sets the device viewport in pixels (QPainter#setViewport). Defaults to the whole bitmap.

Source
set_window(x : Number, y : Number, w : Number, h : Number) : Nil

Sets the logical coordinate window (QPainter#setWindow): subsequent draw calls are in these units. A zero extent is clamped to 1 to stay invertible.

Source
width
Source