一、图像的灰度化处理的基本原理
将彩色图像转化成为灰度图像的过程称为图像的灰度化处理。彩色图像中的每个像素的颜色有R、G、B三个分量决定，而每个分量有255个中值可取，这样一个像素点可以有1600多万（255*255*255）的颜色的变化范围。而灰度图像是R、G、B三个分量相同的一种特殊的彩色图像，其一个像素点的变化范围为255种，所以在数字图像处理中一般先将各种格式的图像转变成灰度图像以使后续的图像的计算量变得少一些。灰度图像的描述与彩色图像一样仍然反映了整幅图像的整体和局部的色度和亮度等级的分布和特征。图像的灰度化处理可用两种方法来实现。
第一种方法是求出每个像素点的R、G、B三个分量的平均值，然后将这个平均值赋予给这个像素的三个分量。
第二种方法是根据YUV的颜色空间中，Y的分量的物理意义是点的亮度，由该值反映亮度等级，根据RGB和YUV颜色空间的变化关系可建立亮度Y与R、G、B三个颜色分量的对应：Y=0.3R+0.59G+0.11B，以这个亮度值表达图像的灰度值。
下面是我的代码：
主窗体的代码:
unit u_main;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ExtCtrls, jpeg, U_Convert;
type
TF_Main = class(TForm)
img1: TImage;
btnSelect: TButton;
dlgOpen1: TOpenDialog;
btnConvertYUV: TButton;
btnConvertRGB: TButton;
procedure btnSelectClick(Sender: TObject);
procedure btnConvertYUVClick(Sender: TObject);
procedure btnConvertRGBClick(Sender: TObject);
procedure FormShow(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
F_Main: TF_Main;
displayFrm:TF_Convert;
implementation
{$R *.dfm}
procedure TF_Main.btnConvertRGBClick(Sender: TObject);
begin
btnConvertYUVClick(Sender);
end;
procedure TF_Main.btnConvertYUVClick(Sender: TObject);
begin
with TF_Convert.Create(Self) do
begin
if TButton(Sender).Name='btnConvertYUV' then
begin
showType:=true;
ShowMessage('采用这样转换方式：计算方式'+#13+
'YUV=0.3R+0.59G+0.11B,新像素点的颜色值：'+#13+
'newR=newG=newB=byte(YUV)');
end
else
if TButton(Sender).Name='btnConvertRGB' then
begin
showType:=False;
ShowMessage('采用这样转换方式：计算方式'+#13+
'tmp=(R+G+B)/3,新像素点的颜色值：'+#13+
'newColor=RGB(tmp,tmp,tmp)');
end;
Caption:=TButton(Sender).Name;
Show;
end;
end;
procedure TF_Main.btnSelectClick(Sender: TObject);
var
img:TImage;
begin
if dlgOpen1.Execute then
begin
img1.Picture.LoadFromFile(dlgOpen1.FileName);
if SameText(ExtractFileExt(dlgOpen1.FileName),'.jpg') then //转换jpg成bmp
begin
try
img:=TImage.Create(Self);
img.Picture.Bitmap.Assign(img1.Picture.Graphic);
img1.Picture.Assign(img.Picture);
img1.Refresh;
finally
img.Free;
end;
end;
end;
end;
procedure TF_Main.FormShow(Sender: TObject);
begin
img1.Picture.Bitmap.LoadFromResourceName(0,'Jay');
end;
end.
显示转换图像的窗体:
unit U_Convert;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
PByteArray = ^TByteArray;
TByteArray = array[0..32767] of Byte;
TF_Convert = class(TForm)
img1: TImage;
procedure FormShow(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
{ Private declarations }
changeBmp,testBmp:TBitmap;
public
showType:Boolean;
{ Public declarations }
end;
var
F_Convert: TF_Convert;
implementation
uses
u_main;
{$R *.dfm}
procedure TF_Convert.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Action:=caFree;
end;
procedure TF_Convert.FormCreate(Sender: TObject);
begin
if not Boolean(changeBmp) then
changeBmp:=TBitmap.Create;
if not Boolean(testBmp) then
testBmp:=TBitmap.Create;
end;
procedure TF_Convert.FormDestroy(Sender: TObject);
begin
if Boolean(changeBmp) then
FreeAndNil(changeBmp );
if Boolean(testBmp) then
FreeAndNil(testbmp);
end;
procedure TF_Convert.FormShow(Sender: TObject);
var
p:PByteArray;
gray,x,y:Integer;
begin
try
testBmp.Assign(F_Main.img1.Picture);//对象赋值
if showType then
begin
for y := 0 to testBmp.Height - 1 do
begin
p:=testBmp.ScanLine[y];
for x := 0 to testBmp.Width - 1 do
begin
gray:=Round(0.3* p[3*x+2]+ 0.59* p[3*x+1]+ 0.11*p[3*x]);//y=0.3R+0.59G+0.11B
//设置新点的颜色值
p[3*x+2]:=Byte(gray);
p[3*x+1]:=Byte(gray);
p[3*x ]:=Byte(gray);
end;
end;
end
else
begin
for y := 0 to testBmp.Height - 1 do
begin
p:=testBmp.ScanLine[y];
for x := 0 to testBmp.Width - 1 do
begin
gray:=Round((p[3*x+2]+p[3*x+1]+p[3*x])/3);//(r+g+b)/3
p[3*x+2]:=gray;
p[3*x+1]:=gray;
p[3*x ]:=gray;
end;
end;
end;
changeBmp.Assign(testBmp);
//显示
img1.Picture.Assign(changeBmp);
img1.Refresh;
except
ShowMessage('格式转换错误');
end;
end;
end.
2个窗体的窗体文件：
object F_Main: TF_Main
Left = 0
Top = 0
Caption = 'MainForm'
ClientHeight = 458
ClientWidth = 426
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
OnShow = FormShow
PixelsPerInch = 96
TextHeight = 13
object img1: TImage
Left = 0
Top = 0
Width = 425
Height = 417
end
object btnSelect: TButton
Left = 343
Top = 425
Width = 75
Height = 25
Caption = #36873#25321#22270#29255
TabOrder = 0
OnClick = btnSelectClick
end
object btnConvertYUV: TButton
Left = 0
Top = 425
Width = 75
Height = 25
Caption = #36716#25442'YUV'
TabOrder = 1
OnClick = btnConvertYUVClick
end
object btnConvertRGB: TButton
Left = 81
Top = 425
Width = 75
Height = 25
Caption = #36716#25442'RGB'
TabOrder = 2
OnClick = btnConvertRGBClick
end
object dlgOpen1: TOpenDialog
Filter = 'bmp|*.bmp|jpeg|*.jpg'
Left = 256
Top = 424
end
end
-------------------------------------------------------------------------------------------------------
object F_Convert: TF_Convert
Left = 0
Top = 0
AutoSize = True
Caption = 'F_Convert'
ClientHeight = 500
ClientWidth = 400
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
OnClose = FormClose
OnCreate = FormCreate
OnDestroy = FormDestroy
OnShow = FormShow
PixelsPerInch = 96
TextHeight = 13
object img1: TImage
Left = 0
Top = 0
Width = 400
Height = 500
Align = alCustom
AutoSize = True
Stretch = True
end
end