如何保存具有透明度的png文件？ [英] How to save a png file with transparency?

问题描述

我正在使用Barcode Studio 2011将QR码绘制到Graphics32 - TImage32组件中，并且我想以png格式保存，但是我在Graphics32的OuterColor中指定了白色透明。

OnFormCreate我刚刚

  procedure TForm1.FormCreate（Sender：TObject）; 
 begin 
 psBarcodeComponent1.BarCode：='some text here ...'; 
结束
  

此刻，我将画作分配给按钮点击事件

  procedure TForm1.Button8Click（Sender：TObject）; //绘制条形码
 var 
 bmp：TBitmap32; 
 Coords：TRect; 
 begin 
 bmp：= TBitmap32.Create; 
 bmp.SetSize（image.Width，image.Height）; 
 bmp.Canvas.Brush.Color：= color; 
 bmp.Canvas.Rectangle（-1，-1，image.Width + 2，image.Height + 2）; 
 
 bmp.DrawMode：= dmTransparent; 
 bmp.OuterColor：= clWhite; 
 
 //使Coord的图像大小
 Coords：= Rect（0,0，image.Width，image.Height）; 
 psBarcodeComponent1.PaintBarCode（bmp.Canvas，Coords）; 
 image.Bitmap.Assign（bmp）; 
结束
  

我正在使用Vampyre Imaging Library将Bitmap转换为PNG格式，但我很乐意使用任何库，功能和建议 - 我一直在试图做这个近一个星期！我已阅读并重读了graphics32的文档以及Vampyre Imaging Library，但是我没有尝试将白色转换为透明的颜色。我已经尝试了clWhite，clWhite32，并将drawMode设置为dmBlend，并将ChromaKey功能全部应用到无效，但很沮丧，咖啡和一点啤酒;）

是我如何保存它...

  procedure TForm1.Button7Click（Sender：TObject）; //保存与Vampyre Imaging Lib 
 {尝试以透明度保存为PNG格式} 
 var 
 FImage：TSingleImage; 
 begin 
 FImage：= TSingleImage.Create; 
 ConvertBitmap32ToImage（image.Bitmap，FImage）; 
 FImage.SaveToFile（'VampyreLibIMG.png'）; 
结束
  

这将导致黑色的缩略图，并在Windows Photo Viewer中查看时完全透明。 p>

我希望我提供足够的信息，有人能够帮助我。

Chris

解决方案

此方法适用于我：

 使用GR32，GR32_PNG，GR32_PortableNetworkGraphic; 
 
 var 
 Y：整数; 
 X：整数; 
 Png：TPortableNetworkGraphic32; 
 
函数IsWhite（Color32：TColor32）：Boolean; 
 begin 
结果：=（TColor32Entry（Color32）.B = 255）和
（TColor32Entry（Color32）.G = 255）和
（TColor32Entry（Color32） 255）; 
结束
 
 begin 
 with Image321 do 
 begin 
 Bitmap.ResetAlpha; 
为Y：= 0到Bitmap.Height-1 do 
 for X：= 0 to Bitmap.Width-1 do 
 begin 
 if IsWhite（Bitmap.Pixel [X， Y]），然后
 Bitmap.Pixel [X，Y]：= Color32（255,255,255,0）; 
结束
 Png：= TPortableNetworkGraphic32.Create; 
 Png.Assign（Bitmap）; 
 Png.SaveToFile（'C：\Temp\NowTransparent.png'）; 
 Png.Free; 
结束
结束
  

这使用 GR32 PNG库。这是一个非常直接的方式，将所有白色像素设置为透明。

PS： Image321 是一个 TImage32 组件，包含我的 TBitmap32 。

I am using Barcode Studio 2011 to paint a QR Code into a Graphics32 - TImage32 Component and I want to save it in png format but with the white colour as transparent this I have specified in the OuterColor of Graphics32.

OnFormCreate I have just

procedure TForm1.FormCreate(Sender: TObject);
begin
  psBarcodeComponent1.BarCode := 'some text here...';
end;

and for the moment I have the painting assigned to a Button Click Event

procedure TForm1.Button8Click(Sender: TObject); // Paint the barcode
var
  bmp: TBitmap32;
  Coords: TRect;
begin
 bmp := TBitmap32.Create;
 bmp.SetSize(image.Width, image.Height);
 bmp.Canvas.Brush.Color := color;
 bmp.Canvas.Rectangle(-1, -1, image.Width+2, image.Height+2);

 bmp.DrawMode := dmTransparent;
 bmp.OuterColor := clWhite;

 // make Coords the size of image
 Coords := Rect(0,0,image.Width,image.Height);
 psBarcodeComponent1.PaintBarCode(bmp.Canvas, Coords);
 image.Bitmap.Assign(bmp);
end;

I am using the Vampyre Imaging Library to convert the Bitmap into PNG Format but I will gladly use any library, function, and advice - I have been trying to do this now for nearly a week! I have read through and re-read the documentation of graphics32 and also of the Vampyre Imaging Library but nothing I try will convert the white to a transparent colour. I have tried clWhite, clWhite32 and also setting the drawMode to dmBlend and applying the ChromaKey Function all to no avail but plenty frustration, coffee and a little beer also ;)

This is how I am saving it...

procedure TForm1.Button7Click(Sender: TObject); // Save with Vampyre Imaging Lib
{ Try to save in PNG format with transparancy }
var
  FImage: TSingleImage;
begin
  FImage := TSingleImage.Create;
  ConvertBitmap32ToImage(image.Bitmap, FImage);
  FImage.SaveToFile('VampyreLibIMG.png');
end;  

This results in a Black coloured thumbnail and when viewed in Windows Photo Viewer it is completely transparent.

I hope that I have provided enough information and that someone is able to help me.

Chris

解决方案

This approach works for me:

uses GR32, GR32_PNG, GR32_PortableNetworkGraphic;

var
  Y: Integer;
  X: Integer;
  Png: TPortableNetworkGraphic32;

  function IsWhite(Color32: TColor32): Boolean;
  begin
    Result:= (TColor32Entry(Color32).B = 255) and
             (TColor32Entry(Color32).G = 255) and
             (TColor32Entry(Color32).R = 255);
  end;

begin
  with Image321 do
  begin
    Bitmap.ResetAlpha;
    for Y := 0 to Bitmap.Height-1 do
      for X := 0 to Bitmap.Width-1 do
      begin
        if IsWhite(Bitmap.Pixel[X, Y]) then
          Bitmap.Pixel[X,Y]:=Color32(255,255,255,0);
      end;
    Png:= TPortableNetworkGraphic32.Create;
    Png.Assign(Bitmap);
    Png.SaveToFile('C:\Temp\NowTransparent.png');
    Png.Free;
  end;
end;

This uses the GR32 PNG library. It's a pretty direct way, setting all white pixels to transparent.

PS: Image321 is a TImage32 component, containing my TBitmap32.

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