绘制透明缩放PNG
Draw Transparent Scaled PNG
我有一张大 (300x300px) PNG 图像,需要重新缩放。在另一个 SO question 中,我阅读了 StretchBlt
和 HALFTONE
以便更好地缩放。
我的问题是如何将 PNG 图像绘制为透明,或者至少将黑角涂成白色?
正如您在所附图片中看到的那样,我得到了黑角。
这是原始图像:
到目前为止,这是我尝试过的。
unit MainU;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
TFormMain = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
FormMain: TFormMain;
implementation
{$R *.dfm}
uses
Pngimage;
type
TIRButton = class(TImage)
protected
procedure Paint; override;
public
constructor Create(AOwner: TComponent); override;
end;
TGraphicControlAcess = class(TGraphicControl);
TGraphicAcess = class(TGraphic);
THalfTonePngImage = class(TPngImage)
protected
procedure Draw(ACanvas: TCanvas; const Rect: TRect); override;
end;
{ TIRButton }
constructor TIRButton.Create(AOwner: TComponent);
begin
inherited;
Center := True;
Proportional := True;
end;
procedure TIRButton.Paint;
var
ParentCanvas: TCanvas;
begin
ParentCanvas := TGraphicControlAcess(Self).Canvas;
TGraphicAcess(Picture.Graphic).Draw(ParentCanvas, DestRect);
end;
{ THalfTonePngImage }
procedure THalfTonePngImage.Draw(ACanvas: TCanvas; const Rect: TRect);
var
p: TPoint;
dc: HDC;
begin
dc := ACanvas.Handle;
GetBrushOrgEx(dc, p);
SetStretchBltMode(dc, HALFTONE);
SetBrushOrgEx(dc, p.X, p.Y, @p);
ACanvas.Brush.Color := clWhite;
ACanvas.FillRect(Classes.Rect(0, 0, Width, Height));
StretchBlt(
dc, 0, Rect.Top, Rect.Right - Rect.Left, Rect.Bottom - Rect.Top,
Canvas.Handle, 0, 0, Width, Height, ACanvas.CopyMode
);
end;
procedure TFormMain.FormCreate(Sender: TObject);
var
Image: THalfTonePngImage;
begin
Image := THalfTonePngImage.Create;
Image.LoadFromFile('X200IR_11_EmgBrake.png');
with TIRButton.Create(Self) do
begin
Width := 100;
Height := 100;
Picture.Assign(Image);
Parent := Self;
Anchors := [akLeft, akTop, akRight, akBottom];
end;
Image.Free;
end;
end.
源图像的角是透明的。由于白色背景,它在正确的图像中不可见。 StretchBlt
不支持透明度。因为它没有,所以透明像素与黑色无法区分。 (如果 ARGB 颜色是 FF 00 00 00
并且我们删除了 alpha 通道,我们剩下 00 00 00
)
您需要使用 TransparentBlt
.
作为参考,这是放置在绿色背景上的图像。更容易看到透明度。
我有一张大 (300x300px) PNG 图像,需要重新缩放。在另一个 SO question 中,我阅读了 StretchBlt
和 HALFTONE
以便更好地缩放。
我的问题是如何将 PNG 图像绘制为透明,或者至少将黑角涂成白色?
正如您在所附图片中看到的那样,我得到了黑角。
这是原始图像:
unit MainU;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
TFormMain = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
FormMain: TFormMain;
implementation
{$R *.dfm}
uses
Pngimage;
type
TIRButton = class(TImage)
protected
procedure Paint; override;
public
constructor Create(AOwner: TComponent); override;
end;
TGraphicControlAcess = class(TGraphicControl);
TGraphicAcess = class(TGraphic);
THalfTonePngImage = class(TPngImage)
protected
procedure Draw(ACanvas: TCanvas; const Rect: TRect); override;
end;
{ TIRButton }
constructor TIRButton.Create(AOwner: TComponent);
begin
inherited;
Center := True;
Proportional := True;
end;
procedure TIRButton.Paint;
var
ParentCanvas: TCanvas;
begin
ParentCanvas := TGraphicControlAcess(Self).Canvas;
TGraphicAcess(Picture.Graphic).Draw(ParentCanvas, DestRect);
end;
{ THalfTonePngImage }
procedure THalfTonePngImage.Draw(ACanvas: TCanvas; const Rect: TRect);
var
p: TPoint;
dc: HDC;
begin
dc := ACanvas.Handle;
GetBrushOrgEx(dc, p);
SetStretchBltMode(dc, HALFTONE);
SetBrushOrgEx(dc, p.X, p.Y, @p);
ACanvas.Brush.Color := clWhite;
ACanvas.FillRect(Classes.Rect(0, 0, Width, Height));
StretchBlt(
dc, 0, Rect.Top, Rect.Right - Rect.Left, Rect.Bottom - Rect.Top,
Canvas.Handle, 0, 0, Width, Height, ACanvas.CopyMode
);
end;
procedure TFormMain.FormCreate(Sender: TObject);
var
Image: THalfTonePngImage;
begin
Image := THalfTonePngImage.Create;
Image.LoadFromFile('X200IR_11_EmgBrake.png');
with TIRButton.Create(Self) do
begin
Width := 100;
Height := 100;
Picture.Assign(Image);
Parent := Self;
Anchors := [akLeft, akTop, akRight, akBottom];
end;
Image.Free;
end;
end.
源图像的角是透明的。由于白色背景,它在正确的图像中不可见。 StretchBlt
不支持透明度。因为它没有,所以透明像素与黑色无法区分。 (如果 ARGB 颜色是 FF 00 00 00
并且我们删除了 alpha 通道,我们剩下 00 00 00
)
您需要使用 TransparentBlt
.
作为参考,这是放置在绿色背景上的图像。更容易看到透明度。