再学 GDI+[103]: TGPImage(23) 提取 GIF 动画的每一帧

本例效果图:

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    ListBox1: TListBox;
    OpenDialog1: TOpenDialog;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure ListBox1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
  img: TGPImage;
  GifFrame, GifFrameCount: Word;

procedure TForm1.FormCreate(Sender: TObject);
begin
  OpenDialog1.Filter := 'GIF 文件|*.gif';
  img := TGPImage.Create;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  img.Free;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  DimensionsCount: Integer;
  DimensionsIDs: PGUID;
  i: Integer;
type
  ArrDimensions = array of TGUID;
begin
  if not OpenDialog1.Execute then Exit;
  img.Free;
  img := TGPImage.Create(OpenDialog1.FileName);

  {获取 Gif 总帧数}
  DimensionsCount := img.GetFrameDimensionsCount;
  GetMem(DimensionsIDs, DimensionsCount * SizeOf(TGUID));
  img.GetFrameDimensionsList(DimensionsIDs, DimensionsCount);
  GifFrameCount := img.GetFrameCount(ArrDimensions(DimensionsIDs)[0]);
  FreeMem(DimensionsIDs);

  Text := Format('共有 %d 帧', [GifFrameCount]);

  {显示帧列表}
  ListBox1.Clear;
  for i := 1 to GifFrameCount do
    ListBox1.Items.Add(Format('第 %d 帧', [i]));

  Repaint;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  g.DrawImage(img, ListBox1.Width + 10, 10, img.GetWidth, img.GetHeight);
  g.Free;
end;

procedure TForm1.ListBox1Click(Sender: TObject);
begin
  GifFrame := ListBox1.ItemIndex;
  img.SelectActiveFrame(FrameDimensionTime, GifFrame);
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 206
  ClientWidth = 339
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
  object ListBox1: TListBox
    Left = 0
    Top = 0
    Width = 89
    Height = 206
    Align = alLeft
    ItemHeight = 13
    TabOrder = 0
    OnClick = ListBox1Click
  end
  object Button1: TButton
    Left = 256
    Top = 173
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 1
    OnClick = Button1Click
  end
  object OpenDialog1: TOpenDialog
    Left = 160
    Top = 104
  end
end