ChartForge4D

A candlestick chart image generator (TradingView style) for Delphi and Free Pascal. It takes plain data arrays and produces a PNG / JPEG / BMP picture of the chart. There is no visual component and no mouse interaction, and it does not depend on any graphics framework (VCL / LCL / FMX / GDI). It works in console programs, services and bots (for example, sending a chart to Telegram).

Features

• Candles, hollow candles, OHLC bars, line, area and Heikin-Ashi
• Volume histogram drawn at the bottom of the main pane
• Any number of separate panes below the chart (RSI, MACD, Stochastic, ...) fed with your own arrays
• Series types: line, step line, histogram, area, dots; horizontal levels (such as 30/70 on RSI), colored bands, and fills between two series (such as Bollinger Bands)
• Drawing tools anchored by time and price, not by candle index: trend line, ray, extended line, horizontal line, horizontal ray, vertical line, rectangle, ellipse, parallel channel, Fibonacci retracement, arrow, text, markers (arrow up/down, circle, square, diamond) and polylines/polygons
• Linear or logarithmic price scale, last-price tag, TradingView-style OHLC legend
• Weighted time axis labels (year > month > day > hour > minute) and a time zone offset
• Dark and light themes, HiDPI output with Scale := 2
• Fully anti-aliased drawing through a built-in software rasterizer and an embedded vector font (Inter), so output does not depend on fonts installed on the machine

Files

File	Purpose
source/ChartForge4D.Types.pas	Types, colors, themes, date/time and number helpers
source/ChartForge4D.Raster.pas	Software canvas and anti-aliased drawing primitives
source/ChartForge4D.FontData.pas	Embedded vector font data (generated)
source/ChartForge4D.Text.pas	Text renderer (replaceable)
source/ChartForge4D.Image.pas	PNG, JPEG and BMP encoders (no VCL needed)
source/ChartForge4D.Scales.pas	Scale math, price ticks and time ticks
source/ChartForge4D.Model.pas	Data model: candles, series, panes, drawings
source/ChartForge4D.Chart.pas	The main class, TCFChart
source/ChartForge4D.Indicators.pas	Optional helpers: SMA, EMA, RSI, MACD, Bollinger, ATR, Stochastic
examples/Delphi/	Self-contained example for Delphi (CFDemo.dpr)
examples/FreePascal/	Self-contained example for Free Pascal / Lazarus (CFDemo.lpr)
LICENSE, NOTICE	Apache License 2.0 and third-party notice

Building

• Delphi XE2 or newer: open examples/Delphi/CFDemo.dpr, or add the source folder to your project's search path.
• Free Pascal 3.0 or newer: run fpc -Mdelphi -Fu../../source CFDemo.lpr inside examples/FreePascal (or open the file in Lazarus and add ../../source to the unit search path).
• To avoid the ZLib dependency, define CF_NO_ZLIB in the conditional defines (PNG files are then written without compression).

Quick start

uses ChartForge4D.Types, ChartForge4D.Model, ChartForge4D.Chart, ChartForge4D.Indicators;

var
  Chart: TCFChart;
  Rsi: TCFDoubleArray;
  PRsi: TCFPane;
begin
  Chart := TCFChart.Create(1600, 900);
  try
    Chart.Title := 'BTCUSDT 1h';
    Chart.SetVisibleBars(150);                 // show the last 150 candles
    // Arrays: unix time (seconds) + Open/High/Low/Close/Volume
    Chart.SetData(Times, Opens, Highs, Lows, Closes, Volumes);

    // Overlay on the price pane (nil = main pane)
    Chart.AddLineSeries(nil, 'MA 20', CFSMA(Closes, 20), CFRGB(255, 152, 0));

    // A separate pane for RSI
    Rsi  := CFRSI(Closes, 14);                 // or an array you calculated yourself
    PRsi := Chart.AddPane('RSI (14)', 1.0);
    PRsi.SetFixedRange(0, 100);
    PRsi.AddLevel(70, CFARGB(150, 120, 123, 134));
    PRsi.AddLevel(30, CFARGB(150, 120, 123, 134));
    Chart.AddLineSeries(PRsi, '', Rsi, CFRGB(126, 87, 194)).ShowLastValue := True;

    // Drawings: start and end are (time, price) pairs
    Chart.AddTrendLine(T1, P1, T2, P2, CFRGB(41, 98, 255), 2.0);

    Chart.SaveToFile('chart.png');             // or .jpg (optional quality) or .bmp
  finally
    Chart.Free;
  end;
end;

Data rules

• Time is an Int64 unix timestamp. The default unit is seconds; for milliseconds (for example Binance data) set Chart.TimeUnit := tuMilliseconds before any other call. Candle times must be strictly increasing.
• If you have TDateTime values, use SetDataDateTime (assumed to be UTC) or CFDateTimeToUnix.
• Volume is optional (there is a SetData overload without it).
• Indicator series are arrays with one value per candle. Use CFNaN for missing values (for example the warm-up period). If your array starts at candle k, set Series.IndexOffset := k.
• If indicator points have their own timestamps, use AddTimedSeries(Pane, Kind, Name, Times, Values, Color).
• A candle whose Open, High, Low or Close is NaN is skipped (it leaves a gap).

Drawing tools

Every Add... method returns a TCFDrawing so you can change its color, width, Style, Text and so on afterwards. The last parameter of each method is APane: nil means the main pane, or pass an indicator pane (for example a trend line on RSI, where the "price" is the RSI value).

Method	Anchors
AddTrendLine, AddRay, AddExtendedLine	2 points (time, price)
AddHorizontalLine, AddHorizontalRay	price (plus a start time for the ray)
AddVerticalLine	time (across all panes or a single pane)
AddRectangle, AddEllipse	two opposite corners
AddParallelChannel	base line (points 1 and 2) plus one point on the parallel line
AddFibRetracement	2 points (level 0 at point 2, level 1 at point 1)
AddArrow, AddText, AddMarker, AddPolyline	see the method declarations

Times that fall between two candles, or after the last candle (the future), are handled: the library interpolates between candles and extrapolates beyond the last one using the typical candle interval.

Main settings

Property	Description
Theme	Colors: CFDarkTheme / CFLightTheme, or change individual fields
ChartStyle	chCandles, chHollowCandles, chOHLC, chLine, chArea, chHeikinAshi
ShowVolume, VolumeHeight	Volume histogram
SetVisibleBars / SetVisibleIndexRange / SetVisibleTimeRange	Visible range
RightPadBars	Empty space on the right (room for drawings in the future)
TimeZoneOffsetMinutes	Time zone used for the time axis labels
LogScale	Logarithmic scale for the price pane
PricePrecision	Number of decimals (default: detected from the data)
Scale, FontSize	Size of all elements; for HiDPI output use Scale := 2 and double Width/Height
Watermark, Title	Background text and legend title

Panes (TCFPane): HeightWeight, SetFixedRange, LogScale, AddLevel, AddBand, AddFill (fill between two series), Decimals.

Limitations

• The built-in font supports ASCII only. For other scripts, derive from TCFTextRenderer and assign your own renderer to Chart.TextRenderer.
• JPEG is written as baseline 4:4:4; PNG is always RGB without transparency.
• "Fill between two series" requires both series to be aligned to candle indexes (not timed series).

Author

Created by Shaahin Ashayeri - https://github.com/DelphiMan68

License

ChartForge4D is released under the Apache License, Version 2.0. See LICENSE and NOTICE.

Font license

The embedded vector font is derived from Inter (SIL Open Font License 1.1). The license text is in docs/Inter-OFL-LICENSE.txt.