我正在尝试根据 article on Embarcadero 访问位图的扫描线。使用像
这样的扫描线for y := 0 to n do
begin
line := bitmap.scanline [y];
for x := 0 to n do line [x] := value;
我之前已经实现过。我注意到访问扫描线需要相对较长的时间,上面提到的文章提供了一个解决方案。我无法正确实现它。我的代码是:
unit SCTester;
interface
uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
ExtCtrls;
type
TRGBQuad = packed record
b: uInt8;
g: uInt8;
r: uInt8;
alpha: uInt8;
end; // Record: TQuad //
// Override the definitions in Graphics.pas
TRGBQuadArray = packed array [0..MaxInt div SizeOf (TRGBQuad) - 1] of TRGBQuad;
PRGBQuadArray = ^TRGBQuadArray;
TForm1 = class(TForm)
Image: TImage;
procedure ImageDblClick(Sender: TObject);
end;
var Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.ImageDblClick(Sender: TObject);
var Bitmap: TBitmap;
q: TRGBQuad;
x, y: NativeInt;
FirstLine: PRGBQuadArray;
idx: NativeInt;
LineLength: NativeInt;
begin
q.r := 0; q.g := 0;
Bitmap := TBitmap.Create;
Bitmap.Height := Image.Height;
Bitmap.Width := Image.Width;
Bitmap.PixelFormat := pf32Bit;
FirstLine := Bitmap.ScanLine [0];
LineLength := (NativeInt (Bitmap.Scanline [1]) - NativeInt (FirstLine)) div SizeOf (TRGBQuad);
try
for y := Bitmap.Height - 1 downto 0 do
begin
for x := 0 to Bitmap.Width - 1 do
begin
q.b := (x xor y) mod 255;
idx := y * LineLength + x;
FirstLine [idx] := q;
end; // for
end; // for
Image.Picture.Assign (Bitmap);
finally
Bitmap.Free;
end; // try..finally
end;
end.
当 y=1 且 x=0 时,我总是会遇到非法访问。 LineLength 为负(位图的宽度),但这可能是预期的。我做错了什么?
编辑:上面的代码已更改,以反射(reflect)迄今为止处理的备注。
最佳答案
为了不访问任何负索引,我会这样做
procedure TForm1.Button1Click(Sender: TObject);
var Bitmap: TBitmap;
q: TRGBQuad;
x, y: LongInt;
line{, FirstLine}: PRGBQuadArray;
idx: NativeInt;
LastLine: PRGBQuadArray;
LineLength: NativeInt;
begin
q.r := 0; q.g := 0;
Bitmap := TBitmap.Create;
Bitmap.Height := Image.Height;
Bitmap.Width := Image.Width;
Bitmap.PixelFormat := pf32Bit;
LastLine := Bitmap.ScanLine[Bitmap.Height - 1];
LineLength := (NativeInt(Bitmap.Scanline[Bitmap.Height - 2]) - NativeInt(Lastline)) div SizeOf(TRGBQuad);
try
for y := 0 to Bitmap.Height - 1 do
begin
for x := 0 to Bitmap.Width - 1 do
begin
q.b := (x xor y) mod 255;
idx := y * LineLength + x;
LastLine [idx] := q;
end; // for
end; // for
Image.Picture.Assign (Bitmap);
finally
Bitmap.Free;
end; // try..finally
end;
关于delphi - 如何正确实现TBitmap的扫描线访问?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10400819/