我需要在我的实际 pascal 项目中将网站转换为透明图像。因此，我将 wkhtmltoimage 的 c 绑定翻译为 pascal（FPC / Lazarus IDE）。这是翻译：
// Copyright 2017 Thorsten Zahn
// translation of wkhtmltox-0.12.4/include/wkhtmltox/image.h -
// Copyright 2010, 2011 wkhtmltopdf authors
//
// pas_libwkhtmltoimage is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// pas_libwkhtmltoimage is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
unit pas_libwkhtmltoimage;
interface
uses
{$IFDEF UNIX}dynlibs,{$ENDIF}
SysUtils, Dialogs;
procedure init_wkhtmltoimage();
procedure init_wkhtmltoimage(install_file: string);
type
PInteger = ^Integer;
wkhtmltoimage_global_settings = record end;
Pwkhtmltoimage_global_settings = ^wkhtmltoimage_global_settings;
wkhtmltoimage_converter = record end;
Pwkhtmltoimage_converter = ^wkhtmltoimage_converter;
wkhtmltoimage_str_callback = procedure (converter:Pwkhtmltoimage_converter; const str:PChar ) cdecl;
wkhtmltoimage_int_callback = procedure (converter:Pwkhtmltoimage_converter; const val:Integer) cdecl;
wkhtmltoimage_void_callback = procedure (converter:Pwkhtmltoimage_converter ) cdecl;
var
wkhtmltoimage_init : function (use_graphics: Integer) : Integer ; cdecl;
wkhtmltoimage_deinit : function () : Integer ; cdecl;
wkhtmltoimage_extended_qt : function () : Integer ; cdecl;
wkhtmltoimage_version : function () : PChar ; cdecl;
wkhtmltoimage_create_global_settings : function () : Pwkhtmltoimage_global_settings; cdecl;
wkhtmltoimage_set_global_setting : function (settings: Pwkhtmltoimage_global_settings; name: PChar; value: PChar) : Integer ; cdecl;
wkhtmltoimage_get_global_setting : function (settings: Pwkhtmltoimage_global_settings; name: PChar; value: PChar; vs: Integer): Integer ; cdecl;
wkhtmltoimage_create_converter : function (settings: Pwkhtmltoimage_global_settings; data: PChar) : Pwkhtmltoimage_converter ; cdecl;
wkhtmltoimage_destroy_converter : procedure(converter: Pwkhtmltoimage_converter) ; cdecl;
wkhtmltoimage_set_warning_callback : procedure(converter: Pwkhtmltoimage_converter; cb: wkhtmltoimage_str_callback) ; cdecl;
wkhtmltoimage_set_error_callback : procedure(converter: Pwkhtmltoimage_converter; cb: wkhtmltoimage_str_callback) ; cdecl;
wkhtmltoimage_set_phase_changed_callback : procedure(converter: Pwkhtmltoimage_converter; cb: wkhtmltoimage_void_callback) ; cdecl;
wkhtmltoimage_set_progress_changed_callback: procedure(converter: Pwkhtmltoimage_converter; cb: wkhtmltoimage_int_callback) ; cdecl;
wkhtmltoimage_set_finished_callback : procedure(converter: Pwkhtmltoimage_converter; cb: wkhtmltoimage_int_callback) ; cdecl;
wkhtmltoimage_convert : function (converter: Pwkhtmltoimage_converter) : Integer ; cdecl;
wkhtmltoimage_current_phase : function (converter: Pwkhtmltoimage_converter) : Integer ; cdecl;
wkhtmltoimage_phase_count : function (converter: Pwkhtmltoimage_converter) : Integer ; cdecl;
wkhtmltoimage_phase_description : function (converter: Pwkhtmltoimage_converter; phase: Integer) : PChar ; cdecl;
wkhtmltoimage_progress_string : function (converter: Pwkhtmltoimage_converter) : PChar ; cdecl;
wkhtmltoimage_http_error_code : function (converter: Pwkhtmltoimage_converter) : Integer ; cdecl;
wkhtmltoimage_get_output : function (converter: Pwkhtmltoimage_converter; _para2: PPbyte) : Integer ; cdecl;
implementation
var
lib_handle : THandle;
procedure handle_error(error: string);
begin
ShowMessage(error);
end;
function lib_get_proc_addr(var addr: Pointer; const name : PAnsiChar) : Boolean;
begin
{$IFDEF UNIX}
addr := GetProcedureAddress(lib_handle, name);
{$ENDIF}
{$IFDEF MSWINDOWS}
addr := GetProcAddress(libvlc_handle, name);
{$ENDIF}
result := (addr <> NIL);
if not result then
begin
handle_error('Procedure "' + name + '" not found!');
end;
end;
procedure init_wkhtmltoimage();
begin
if (lib_handle <> 0) then exit;
init_wkhtmltoimage('<path to lib>/libwkhtmltox.so.0.12.4');
end;
procedure init_wkhtmltoimage(install_file: string);
begin
if (lib_handle <> 0) then exit;
//load lib
{$IFDEF SUPPORTS_UNICODE}
lib_handle := LoadLibrary(PWideChar(install_file));
{$ELSE}
lib_handle := LoadLibrary(PAnsiChar(install_file));
{$ENDIF}
//error?
if (lib_handle = 0) then
begin
handle_error(
'Library not found ' + install_file + ', ' +
{$IFDEF UNIX}
'GetLastError() = ' + IntToStr(GetLastOSError())
{$ENDIF}
{$IFDEF MSWINDOWS}
'GetLastError() = ' + IntToStr(GetLastError())
{$ENDIF}
);
exit;
end;
//get_proc_addr
if not lib_get_proc_addr(pointer(wkhtmltoimage_init ), 'wkhtmltoimage_init' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_deinit ), 'wkhtmltoimage_deinit' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_extended_qt ), 'wkhtmltoimage_extended_qt' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_version ), 'wkhtmltoimage_version' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_create_global_settings ), 'wkhtmltoimage_create_global_settings' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_global_setting ), 'wkhtmltoimage_set_global_setting' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_get_global_setting ), 'wkhtmltoimage_get_global_setting' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_create_converter ), 'wkhtmltoimage_create_converter' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_destroy_converter ), 'wkhtmltoimage_destroy_converter' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_warning_callback ), 'wkhtmltoimage_set_warning_callback' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_error_callback ), 'wkhtmltoimage_set_error_callback' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_phase_changed_callback ), 'wkhtmltoimage_set_phase_changed_callback' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_progress_changed_callback), 'wkhtmltoimage_set_progress_changed_callback') then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_set_finished_callback ), 'wkhtmltoimage_set_finished_callback' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_convert ), 'wkhtmltoimage_convert' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_current_phase ), 'wkhtmltoimage_current_phase' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_phase_count ), 'wkhtmltoimage_phase_count' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_phase_description ), 'wkhtmltoimage_phase_description' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_progress_string ), 'wkhtmltoimage_progress_string' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_http_error_code ), 'wkhtmltoimage_http_error_code' ) then exit;
if not lib_get_proc_addr(pointer(wkhtmltoimage_get_output ), 'wkhtmltoimage_get_output' ) then exit;
end;
end.
我正在使用 libwkhtmltox.so.0.12.4。首先，我尝试使用如下代码创建一个 bmp 图像：
unit Unit1;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
ExtCtrls, testlib;
type
{ TForm1 }
TForm1 = class(TForm)
Button1: TButton;
Image1: TImage;
procedure Button1Click(Sender: TObject);
private
{ private declarations }
public
{ public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.lfm}
{ TForm1 }
//(callback procedures removed in this example)
procedure TForm1.Button1Click(Sender: TObject);
var
gs: Pwkhtmltoimage_global_settings;
c: Pwkhtmltoimage_converter;
data: PByte;
len: Integer;
stream: TMemoryStream;
i: Integer;
begin
init_wkhtmltoimage();
wkhtmltoimage_init(Integer(false));
gs := wkhtmltoimage_create_global_settings();
wkhtmltoimage_set_global_setting(gs, 'in' , 'http://www.google.com/');
//wkhtmltoimage_set_global_setting(gs, 'fmt', 'jpeg');
wkhtmltoimage_set_global_setting(gs, 'fmt', 'bmp');
//wkhtmltoimage_set_global_setting(gs, 'fmt', 'svg');
c := wkhtmltoimage_create_converter(gs, nil);
//(callback procedures removed in this example)
//wkhtmltoimage_set_progress_changed_callback(c, @progress_changed);
//wkhtmltoimage_set_phase_changed_callback (c, @phase_changed);
//wkhtmltoimage_set_error_callback (c, @error);
//wkhtmltoimage_set_warning_callback (c, @warning);
if not Boolean(wkhtmltoimage_convert(c)) then
begin
ShowMessage('Conversion failed!');
exit;
end;
len := wkhtmltoimage_get_output(c, @data);
stream := TMemoryStream.Create();
for i:=0 to len-1 do
stream.Write((data+i)^, 1);
stream.Position:=0;
Image1.Picture.LoadFromStream(stream);
stream.SaveToFile('/home/thorsten/Test.png');
stream.Free;
wkhtmltoimage_destroy_converter(c);
wkhtmltoimage_deinit();
end;
end.
这工作正常。jpeg 和 svg 格式也可以使用（对于使用 svg，必须引用 Image1 中的显示）。使用 svg 时，透明背景选项也可以使用 ( wkhtmltoimage_set_global_setting(gs, 'transparent', 'true');)。但是如果我尝试 png ( wkhtmltoimage_set_global_setting(gs, 'fmt', 'png');) 我会收到错误Could not save image（通过回调）。
可能是什么问题？这个问题在c代码中也存在吗？
谢谢
我也测试了控制台工具（从 Ubuntu 存储库安装，版本 0.12.2.4-1）。这个工具有效。但如果我要使用这个工具，我必须保存临时文件。