fcl-image

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Introduction

FCL-Image started life as "fpimage", pretty much as an attempt to implement a generally portable TImage like class, without the deep win32 and VCL ties.

Current file list

The central units are fpimage and fpcanvas and these are further enhanced by OOP derivation.

  • bmpcomn A few structures and constants for the BMP fileformat
  • clipping Some utility routines that help with clipping and intersecting of rects.
  • ellipses Drawing of ellipses and arcs, and filling ellipses and pies.
    • TEllipseInfo
  • extinterpolation interpolation filters for TFPCanvas.StretchDraw (
    • TBlackmanInterpolation
    • TBlackmanSincInterpolation
    • TBlackmanBesselInterpolation
    • TGaussianInterpolation
    • TBoxInterpolation
    • THermiteInterpolation
    • TLanczosInterpolation
    • TQuadraticInterpolation
    • TCubicInterpolation
    • TCatromInterpolation
    • TBilineairInterpolation
    • THanningInterpolation
    • THammingInterpolation
  • fpcanvas Generic Canvas classes.
    • TFPCanvasException
    • TFPPenException
    • TFPBrushException
    • TFPFontException
    • TFPCustomCanvas
    • TFPCanvasHelper
    • TFPCustomFont
    • TFPCustomFontClass
    • TFPCustomPen
    • TFPCustomPenClass
    • TFPCustomBrush
    • TFPCustomBrushClass
    • TFPCustomInterpolation
    • TFPBaseInterpolation
    • TMitchelInterpolation
    • TFPCustomCanvas
    • TFPCustomDrawFont
    • TFPEmptyFont
    • TFPCustomDrawPen
    • TFPEmptyPen
    • TFPCustomDrawBrush
    • TFPEmptyBrush
  • fpcolhash an implementation of a color hash table.
    • TFPColorHashException
    • TFPColorHashTable
  • fpditherer contains classes used to dither images.
    • FPDithererException
    • TFPBaseDitherer
    • TFPFloydSteinbergDitherer
  • fpimage fpImage base definitions and classes
    • TFPCustomImageReader
    • TFPCustomImageWriter
    • TFPCustomImage
    • FPImageException
    • TFPPalette
    • TFPCustomImage
    • TFPMemoryImage
    • TFPCustomImageHandler
    • TFPCustomImageReader
    • TFPCustomImageWriter
    • TIHData
    • TImageHandlersManager
  • fpimgcanv Image Canvas - canvas which draws on an image.
    • TFPImageCanvas
  • fpimgcmn Image Common: small procedural Helpers (swap,crc)
  • fppixlcanv
    • TPixelCanvas
  • fpquantizer classes used to quantize images. See [1]
  • freetype Encapsulating classes over freetype
  • freetypeh Freetype header translation
  • ftfont More freetype related font classes
  • pcxcomn PCX fileformat records and types
  • pixtools Pixel drawing routines.
  • pngcomn PNG fileformat records and types
  • pscanvas TPostScriptCanvas implementation.
  • targacmn Targa fileformat records and types

Readers and writers for various image formats

  • fpreadbmp
  • fpreadjpeg
  • fpreadpcx
  • fpreadpng
  • fpreadpnm
  • fpreadtga
  • fpreadtiff
  • fpreadxpm
  • fpwritebmp
  • fpwritejpeg
  • fpwritepcx
  • fpwritepng
  • fpwritepnm
  • fpwritetga
  • fpwritetiff
  • fpwritexpm

INC files uses in fpcanvas

  • fpbrush
  • fpcanvas
  • fpcdrawh
  • fpfont
  • fphelper
  • fpinterpolation
  • fppen

INC files uses in fpmake

  • fpcolors
  • fpimage
  • fphandler
  • fpcolcnv
  • fppalette

Demoes

  • drawing
  • imgconv

Known Issues and limitations

  • fcl-image is written for maximal portability and maintainability and is quite slow. The main storage type is 16-bit RGBA, storing always 64-bit per pixel, and a function is called to get each pixel.
  • pngwriter doesn't implement automatic detection of filters, and thus is always "filter none"
  • most writers don't autodetect what format to save. You must correctly set the relevant writer options ( see also bug 17621).
  • the color format can be counter intuitive, read this thread
  • png only implements basic chunk types (idat,trns,plte,ihdr and iend). It e.g. can't handle chunks like pHYs,iCCP,gAMA,cHRM yet. (bug 19209).

Image formats

Here is a table with the correct class to use for each image format, as well as comparing to the LCL.

Format fcl-image reader unit fcl-image writer unit LCL class
Windows Bitmap. A very simple format, usually used without compression and without transparency, but it may also have them, although many applications don't support those extra features. (*.bmp) fpreadbmp fpwritebmp TBitmap
A popular format for websites. It supports up to 8 bits per pixels, which are 256 distinct colors chosen from the 24-bit RGB color space. This limitation makes it unsuitable for complex images, but useful for simple graphics. The image is compressed without loss in quality and the format also supports animations. (*.gif) fpreadgif - TGIFImage
The most popular format for websites, and an ISO standard since 1994. The format compressed the image but generates a small loss of quality. (*.jpeg, *.jpg) fpreadjpeg fpwritejpeg TJpegImage
A format widely used in DOS applications, but now less popular. (*.pcx) fpreadpcx fpwritepcx -
Portable Network Graphics. A popular format for it's efficient compression without quality loss. (*.png) fpreadpng fpwritepng TPortableNetworkGraphic
Supports the formats Portable BitMaps (*.pbm), Portable GrayMaps (*.pgm) and Portable PixMaps (*.ppm) fpreadpnm fpwritepnm TPortableAnyMapGraphic
The default file format for Adobe Photoshop® (*.pds) fpreadpsd - -
Called either Truevision TGA File Format or TARGA File Format, this is a compressed format commonly used in games. (*.tga, *.tpic) fpreadtga fpwritetga -
Tagged Image File Format (TIFF), originally created to have a common image format for scanners. (*.tiff, *.tif). Controlled by Adobe® fpreadtiff fpwritetiff TTiffImage
X PixMap, an image format used by the X Window System which stores the data in ASCII text. Is also used as an icon format in UNIX applications. (*.xpm) fpreadxpm fpwritexpm TPixmap
X Window Dump file format. Used by the program xwd which generates screenshots in the X Window System. (*.xwd) fpreadxwd - -
Windows Icon. Is a list of small bitmaps in various color depths and sizes, with transparency support and no compression. (*.ico) - - TIcon
Windows Cursor. Exactly the same format as the Windows Icon, but with an extra field in the header for the cursor hotspot. (*.cur) - - TCursorImage
Mac OS X icon. List of small images in various sizes. (*.icns) - - TIcnsIcon

Tiff

Working features of the reader:

  • Black and white/lineart/1 bit (FPC trunk only, not in FPC 2.6.x)
  • Grayscale 8,16bit (optional alpha),
  • RGB 8,16bit (optional alpha),
  • Orientation, except for rotated orientation
  • compression: packbits, LZW, deflate
  • endian
  • multiple images/multipage
  • strips and tiles
  • Sets properties in the image Extras properties, which is used by the writer, so that reading/writing keeps many common tags like Artist, Copyright, DateAndTime, HostComputer, ImageDescription, Maker, Model, Software, DocumentName, XResolution, YResolution, Orientation, bit depts, page name, isThumbnail.

Here is an incomplete list of open / not yet implemented features of the reader:

  • Compression: jpeg, CCITT Group 3, CCITT Group 4
  • PlanarConfiguration 2
  • ColorMap
  • separate mask
  • fillorder - not needed by baseline tiff reader
  • bigtiff 64bit offsets
  • XMP tag 700
  • ICC profile tag 34675
  • Orientation with rotation

Working features of the writer:

  • Grayscale 8,16bit (optional alpha)
  • RGB 8,16bit (optional alpha)
  • Orientation except rotated
  • multiple images, pages
  • thumbnail
  • Compression: deflate

Here is an incomplete list of open / not yet implemented features of the writer:

  • Compression: LZW, packbits, jpeg, CCIT Group 3,CCIT Group 4,...
  • Planar
  • ColorMap
  • separate mask
  • fillorder - not needed by baseline tiff reader
  • bigtiff 64bit offsets
  • endian - currently using system endianess
  • Orientation with rotation

Walk-through

Basic Canvas Setup

You'll need a few things to start up. A canvas, image, and writer. The writer is to write images like PNG. The sample below will give you a 100x100 black png.

{$mode objfpc}{$h+}
program demo;
 
uses classes, sysutils,
     FPImage, FPCanvas, FPImgCanv,
     FPWritePNG;
 
var canvas : TFPCustomCanvas;
    image : TFPCustomImage;
    writer : TFPCustomImageWriter;
begin
  { Create an image 100x100 pixels}
  image := TFPMemoryImage.Create (100,100);
 
  { Attach the image to the canvas }
  Canvas := TFPImageCanvas.Create (image);
 
  { Create the writer }
  Writer := TFPWriterPNG.Create;
 
  { Save to file }
  image.SaveToFile ('DrawTest.png', writer);
 
  { Clean up! }
  Canvas.Free;
  image.Free;
  writer.Free;
end.

Drawing a Circle

Drawing a circle requires a bit more then just giving a width. You'll need to setup the pen style, mode, width, and color to do this. FCL-Image comes with a few pen modes and styles, it will really be up to you to decide which you'll need. Its best for now to try with a few modes and styles to get a better understanding of what FCL-Image can do.


{$mode objfpc}{$h+}
program demo;
 
uses classes, sysutils,
     FPImage, FPCanvas, FPImgCanv,
     FPWritePNG;
 
var canvas : TFPcustomCanvas;
    image : TFPCustomImage;
    writer : TFPCustomImageWriter;
    { 
      Colors range from 0 to 65535 in each primary color. 
      They can also show as hexideciaml:
      $FFFF = 65535, $0000 = 0 
    }
    passionRed: TFPColor = (Red: 65535; Green: 0; Blue: 0; Alpha: 65535);
begin
  image := TFPMemoryImage.Create (100,100);
  Canvas := TFPImageCanvas.Create (image);
  Writer := TFPWriterPNG.Create;
 
  { Set the pen styles }
  with canvas do
  begin
    pen.mode    := pmCopy;
    pen.style   := psSolid;
    pen.width   := 1;
    pen.FPColor := passionRed;
  end;
 
  { Draw a circle }
  canvas.Ellipse (10,10, 90,90);
 
  { Save to file }
  image.SaveToFile ('DrawTest.png', writer);
 
  { Clean up! }
  Canvas.Free;
  image.Free;
  writer.Free;
end.

Pen Modes

The pen mode is how the pixel drawn will react to the pixels beneath it. So if its a white pixel and you draw a red pixel over it with the mode of pmXor then you'll get a vibrate blue pixel.

  • pmBlack
  • pmWhite
  • pmNop
  • pmNot
  • pmCopy
  • pmNotCopy
  • pmMergePenNot
  • pmMaskPenNot
  • pmMergeNotPen
  • pmMaskNotPen
  • pmMerge
  • pmNotMerge
  • pmMask
  • pmNotMask
  • pmXor
  • pmNotXor


Pen Styles

  • psSolid
  • psDash
  • psDot
  • psDashDot
  • psDashDotDot
  • psinsideFrame
  • psPattern
  • psClear

Drawing text

Here is an example, how to create a 200x100 image, painting a white background and some text and saving it as .png:

program fontdraw;
 
{$mode objfpc}{$H+}
 
uses
  Classes, SysUtils, FPimage, FPImgCanv, ftfont, FPWritePNG, FPCanvas;
 
procedure TestFPImgFont;
var
  Img: TFPMemoryImage;
  Writer: TFPWriterPNG;
  ms: TMemoryStream;
  ImgCanvas: TFPImageCanvas;
  fs: TFileStream;
  AFont: TFreeTypeFont;
begin
  Img:=nil;
  ImgCanvas:=nil;
  Writer:=nil;
  ms:=nil;
  fs:=nil;
  AFont:=nil;
  try
    // initialize free type font manager
    ftfont.InitEngine;
    FontMgr.SearchPath:='/usr/share/fonts/truetype/ttf-dejavu/';
    AFont:=TFreeTypeFont.Create;
 
    // create an image of width 200, height 100
    Img:=TFPMemoryImage.Create(200,100);
    Img.UsePalette:=false;
    // create the canvas with the drawing operations
    ImgCanvas:=TFPImageCanvas.create(Img);
 
    // paint white background
    ImgCanvas.Brush.FPColor:=colWhite;
    ImgCanvas.Brush.Style:=bsSolid;
    ImgCanvas.Rectangle(0,0,Img.Width,Img.Height);
 
    // paint text
    ImgCanvas.Font:=AFont;
    ImgCanvas.Font.Name:='DejaVuSans';
    ImgCanvas.Font.Size:=20;
    ImgCanvas.TextOut(10,30,'Test');
 
    // write image as png to memory stream
    Writer:=TFPWriterPNG.create;
    ms:=TMemoryStream.Create;
    writer.ImageWrite(ms,Img);
    // write memory stream to file
    ms.Position:=0;
    fs:=TFileStream.Create('testfont.png',fmCreate);
    fs.CopyFrom(ms,ms.Size);
  finally
    AFont.Free;
    ms.Free;
    Writer.Free;
    ImgCanvas.Free;
    Img.Free;
    fs.Free;
  end;
end;
 
begin
  TestFPImgFont;
end.

Reading an image file

It is very easy to read image files with fcl-image, as the example below shows:

uses
  fpreadgif, fpimage;
 
var
  image: TFPCustomImage;
  reader: TFPCustomImageReader;
begin
  Image := TFPMemoryImage.Create(10, 10);
  Reader := TFPReaderGIF.Create;
  Image.LoadFromFile(AFileName, Reader);
  // ...

Converting between two raster image formats

To convert simply open in one format and save in the desired one, like in this example:

uses
  fpreadgif, fpimage, fpwritebmp;
 
var
  image: TFPCustomImage;
  reader: TFPCustomImageReader;
  writer: TFPCustomImageWriter;
begin
  Image := TFPMemoryImage.Create(10, 10);
  Reader := TFPReaderGIF.Create;
  Writer := TFPWriterBMP.Create;
 
  Image.LoadFromFile(AFileName, Reader);
  Image.SaveToFile(ADestFileName, Writer);
  //...

See also