图像缩放是最常用的图像处理，在图像拉伸和取得图像略图中都要用到。图像缩放质量的好坏与图像像素插值方式有关，本文定义了常用的3种插值方式，即临近插值、线性插值和双立方插值方式：
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type
// 插值方式: 缺省(线性插值)，临近，线性，双立方
TInterpolateMode = (imDefault, imNear, imBilinear, imBicubic);
type
// 插值方式: 缺省(线性插值)，临近，线性，双立方
TInterpolateMode = (imDefault, imNear, imBilinear, imBicubic);
具体的缩放及其用到的插值过程代码如下：
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过程定义：
// 设置双立方插值的斜率。缺省值为-0.75
procedure SetBicubicSlope(const Value: Single);
// 缩放图像，IpMode插值方式
procedure ImageScale(Dest: TImageData; const Source: TImageData;
IpMode: TInterpolateMode = imDefault); overload;
// Source分别按比例ScaleX和ScaleY缩放到Dest的(x,y)坐标，IpMode插值方式
procedure ImageScale(Dest: TImageData; x, y: Integer; const Source: TImageData;
ScaleX, ScaleY: Single; IpMode: TInterpolateMode = imDefault); overload;
// TGraphic对象缩放到Dest
procedure ImageScale(Dest: TImageData; const Source: TGraphic;
IpMode: TInterpolateMode = imDefault); overload;
procedure ImageScale(Dest: TImageData; x, y: Integer; const Source: TGraphic;
ScaleX, ScaleY: Single; IpMode: TInterpolateMode = imDefault); overload;
// TGpBitmap对象缩放到Dest
procedure ImageScale(Dest: TImageData;
const Source: TGpBitmap; IpMode: TInterpolateMode = imDefault); overload;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGpBitmap; ScaleX, ScaleY: Single;
IpMode: TInterpolateMode = imDefault); overload;
实现代码：
type
TInterpolateProc = procedure;
var
BicubicTable: Pointer;
BicubicSlope: Single;
BilinearTable: Pointer;
(*****************************************************************************
* typedef UINT ARGB *
* ARGB GetBilinearColor(int x(*256), int y(*256), void* Scan0, UINT Stride) *
* *
* int x0 = x / 256 *
* int y0 = y / 256 *
* BYTE *pScan0 = Scan0 + y0 * Stride + y0 * 4 *
* BYTE c[4][4] *
* c[0] = *pScan0 // (x0, y0) *
* c[1] = *(pScan0 + Stride) // (x0, y0+1) *
* c[2] = *(pScan0 + 4) // (x0+1, y0) *
* c[3] = *(PScan0 + Stride + 4) // (x0+1, y0+1) *
* int u = x & 0xff *
* int v = y & 0xff *
* int m0 = (255-v) * (255-u) *
* int m1 = v * (255-u) *
* int m2 = (255-v) * u *
* int m3 = v * u *
* BYTE ARGB[4] *
* for (int i = 0; i < 4; i ++) *
* ARGB[i] = (c[0][i]*m0 + c[1][i]*m1 + c[2][i]*m2 + c[3][i]*m3) / 65536 *
*****************************************************************************)
procedure GetBilinearColor;
asm
and edx, 255
and ecx, 255
shl edx, 4
shl ecx, 4
mov eax, BilinearTable
movq mm0, [esi] // mm0 = C2 (x0+1, y0) C0(x0, y0)
movq mm1, mm0
add esi, [ebx].TImageData.Stride
// [esi] = C3(x0+1, y0+1) C1(x0, y0+1)
punpcklbw mm0, [esi] // mm0 = A1 A0 R1 R0 G1 G0 B1 B0
punpckhbw mm1, [esi] // mm1 = A3 A2 R3 R2 G3 G2 B3 B2
movq mm2, mm0
movq mm3, mm1
punpcklbw mm0, mm7 // mm0 = 00 G1 00 G0 00 B1 00 B0
punpcklbw mm1, mm7 // mm1 = 00 G3 00 G2 00 B3 00 B2
punpckhbw mm2, mm7 // mm2 = 00 A1 00 A0 00 R1 00 R0
punpckhbw mm3, mm7 // mm3 = 00 A3 00 A2 00 R3 00 R2
movq mm4, [eax + edx]
pmullw mm4, [eax + ecx + 8]
psrlw mm4, 1 // 先除以2，否则后面的word有符号乘法会扩展符号位
movq mm5, mm4
punpckldq mm4, mm4 // mm4 = 00 m1 00 m0 00 m1 00 m0
punpckhdq mm5, mm5 // mm5 = 00 m3 00 m2 00 m3 00 m2
pmaddwd mm0, mm4 // mm0 = G1*m1+G0*m0 B1*m1+B0*m0
pmaddwd mm1, mm5 // mm1 = G3*m3+G2*m2 B3*m3+B2*m2
pmaddwd mm2, mm4 // mm2 = A1*m1+A0*m0 R1*m1+R0*m0
pmaddwd mm3, mm5 // mm3 = A3*m3+A2*m2 R3*m3+R2*m2
paddd mm0, mm1 // mm0 = G3n+G2n+G1n+G0n B3n+B2n+B1n+B0n
paddd mm2, mm3 // mm2 = A2n+A2n+A1n+A0n R3n+R2n+R1n+R0n
psrld mm0, 15 // mm0 = Gn/0x8000 Bn/0x8000
psrld mm2, 15 // mm2 = An/0x8000 Rn/0x8000
packssdw mm0, mm2 // mm0 = 00 An 00 Rn 00 Gn 00 Bn
packuswb mm0, mm0 // mm0 = An Rn Gn Bn An Rn Gn Bn
end;
procedure GetNearColor;
asm
movd mm0, [esi]
end;
procedure GetBicubicColor;
procedure SumBicubic;
asm
movd mm1, [esi]
movd mm2, [esi + 4]
movd mm3, [esi + 8]
movd mm4, [esi + 12]
punpcklbw mm1, mm7
punpcklbw mm2, mm7
punpcklbw mm3, mm7
punpcklbw mm4, mm7
psllw mm1, 7
psllw mm2, 7
psllw mm3, 7
psllw mm4, 7
pmulhw mm1, [edi + 256 * 8 + edx]
pmulhw mm2, [edi + edx]
pmulhw mm3, [edi + 256 * 8 + eax]
pmulhw mm4, [edi + 512 * 8 + eax]
paddsw mm1, mm2
paddsw mm3, mm4
paddsw mm1, mm3
pmulhw mm1, mm5
paddsw mm0, mm1
add esi, [ebx].TImageData.Stride
end;
asm
push edi
mov edi, BicubicTable// edi = int64 uvTable (item * 16384)
and edx, 255 // u = x & 255
shl edx, 3 // edx = u * 8
mov eax, edx // eax = -edx
neg eax
and ecx, 255 // v = y & 255
shl ecx, 3 // ecx = v * 8
pxor mm0, mm0
movq mm5, [edi + 256 * 8 + ecx]
call SumBicubic
movq mm5, [edi + ecx]
call SumBicubic
neg ecx
movq mm5, [edi + 256 * 8 + ecx]
call SumBicubic
movq mm5, [edi + 512 * 8 + ecx]
call SumBicubic
paddw mm0, mm6 // argb += 4
psraw mm0, 3 // argb /= 8
packuswb mm0, mm0
pop edi
end;
procedure AlphaBlendPixel;
asm
// movd mm0, eax // mm0 = 00 00 00 00 As Rs Gs Bs
movd mm1, [edi] // mm1 = 00 00 00 00 Ad Rd Gd Bd
punpcklbw mm0, mm7 // mm0 = 00 As 00 Rs 00 Gs 00 Bs
punpcklbw mm1, mm7 // mm1 = 00 Ad 00 Rd 00 Gd 00 Bd
movq mm2, mm0
punpckhwd mm2, mm2
punpckhdq mm2, mm2 // mm2 = Alpha Alpha Alpha Alpha
psubw mm0, mm1 // mm0 = As-Ad Rs-Rd Gs-Gd Bs-Bd
pmullw mm0, mm2 // mm0 = As*Alpha Rs*Alpha Gs*Alpha Bs*Alpha
psllw mm1, 8 // mm1 = Ad*256 Rd*256 Gd*256 Bd*256
paddw mm0, mm1 // mm0 = 00 An 00 Rn 00 Gn 00 Bn
psrlw mm0, 8 // mm0 = An/256 Rn/256 Gn/256 Bn/256
packuswb mm0, mm7 // mm0 = 00 00 00 00 An Rn Gn Bn
movd [edi], mm0
end;
function GetInterpolateProc(IpMode: TInterpolateMode; var Proc: TInterpolateProc): Integer;
begin
case IpMode of
imNear:
begin
Result := 1;
Proc := GetNearColor;
end;
imBicubic:
begin
Result := 4;
Proc := GetBicubicColor;
end
else
begin
Result := 2;
Proc := GetBilinearColor;
end;
end;
end;
procedure ImageScale(Dest: TImageData; const Source: TImageData; IpMode: TInterpolateMode);
var
x, y: Integer;
Width, Height: Integer;
xDelta, yDelta: Integer;
Radius, dstOffset: Integer;
src: TImageData;
GetColor: TInterpolateProc;
procedure DoScale(dst: TImageData);
asm
pxor mm7, mm7
mov edx, 04040404h
movd mm6, edx
punpcklbw mm6, mm7
lea edx, src
push edx
call SetDataCopyReg
imul ecx, xDelta
imul edx, yDelta
add ecx, x
add edx, y
mov Width, ecx
mov Height, edx
mov dstOffset, ebx
pop ebx
mov ecx, y // for (; y < Height; y ++){
@yLoop: // {
mov esi, ecx
sar esi, 8 // esi = Source.Scan0 + y / 256 * Source.Stride
imul esi, [ebx].TImageData.Stride
add esi, [ebx].TImageData.Scan0
mov edx, x // for (; x < Width; x ++){
@xLoop: // {
push esi
push edx
push ecx
mov eax, edx
sar eax, 8
shl eax, 2
add esi, eax // esi += (x / 256 * 4)
call GetColor // mm0 = GetColor(src, esi, x, y)
call AlphaBlendPixel // AlphaBlendPixel(mm0, edi)
add edi, 4 // edi += 4
pop ecx
pop edx
pop esi
add edx, xDelta // x0 += xDelta
cmp edx, Width
jl @xLoop // }
add edi, dstOffset // edi += dstOffset
add ecx, yDelta // y0 += yDelta
cmp ecx, Height
jl @yLoop // }
emms
end;
begin
Radius := GetInterpolateProc(IpMode, GetColor);
xDelta := (Source.Width shl 8) div Dest.Width;
yDelta := (Source.Height shl 8) div Dest.Height;
x := (xDelta{ shr 1}) + (Radius shl 7);
y := (yDelta{ shr 1}) + (Radius shl 7);
src := ImageGetExpandData(Source, 0, 0, Source.Width, Source.Height, Radius);
try
DoScale(Dest);
finally
FreeImageData(src);
end;
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TImageData; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src, dst: TImageData;
begin
if not ((ScaleX > 0.0) and (ScaleY > 0.0)) then
Exit;
dst := GetSubImageData(Dest, x, y, Round(Source.Width * ScaleX),
Round(Source.Height * ScaleY));
if ImageEmpty(dst) then Exit;
if x < 0 then x := -Trunc(x / ScaleX) else x := 0;
if y < 0 then y := -Trunc(y / ScaleY) else y := 0;
src := GetSubImageData(Source, x, y, Round(dst.Width / ScaleX),
Round(dst.Height / ScaleY));
ImageScale(dst, src, IpMode);
end;
procedure ImageScale(Dest: TImageData; const Source: TGraphic;
IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, src, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGraphic; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, x, y, src, ScaleX, ScaleY, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData;
const Source: TGpBitmap; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, src, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGpBitmap; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, x, y, src, ScaleX, ScaleY, IpMode);
FreeImageData(src);
end;
procedure SetBicubicSlope(const Value: Single);
type
TBicArray = array[0..3] of Smallint;
PBicArray = ^TBicArray;
var
I: Integer;
P: PBicArray;
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0.0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1.0 then
Result := (Value + 2.0) * x3 - (Value + 3.0) * x2 + 1.0
else if x <= 2.0 then
Result := Value * x3 - (5.0 * Value) * x2 + (8.0 * Value) * x - (4.0 * Value)
else Result := 0.0;
end;
begin
if (BicubicSlope <> Value) and (Value < 0.0) {and (Value >= -2.0)} then
begin
BicubicSlope := Value;
P := BicubicTable;
for I := 0 to 512 do
begin
P^[0] := Round(16384 * BicubicFunc(I * (1.0 / 256)));
P^[1] := P^[0];
P^[2] := P^[0];
P^[3] := P^[0];
Inc(P);
end;
end;
end;
过程定义：
// 设置双立方插值的斜率。缺省值为-0.75
procedure SetBicubicSlope(const Value: Single);
// 缩放图像，IpMode插值方式
procedure ImageScale(Dest: TImageData; const Source: TImageData;
IpMode: TInterpolateMode = imDefault); overload;
// Source分别按比例ScaleX和ScaleY缩放到Dest的(x,y)坐标，IpMode插值方式
procedure ImageScale(Dest: TImageData; x, y: Integer; const Source: TImageData;
ScaleX, ScaleY: Single; IpMode: TInterpolateMode = imDefault); overload;
// TGraphic对象缩放到Dest
procedure ImageScale(Dest: TImageData; const Source: TGraphic;
IpMode: TInterpolateMode = imDefault); overload;
procedure ImageScale(Dest: TImageData; x, y: Integer; const Source: TGraphic;
ScaleX, ScaleY: Single; IpMode: TInterpolateMode = imDefault); overload;
// TGpBitmap对象缩放到Dest
procedure ImageScale(Dest: TImageData;
const Source: TGpBitmap; IpMode: TInterpolateMode = imDefault); overload;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGpBitmap; ScaleX, ScaleY: Single;
IpMode: TInterpolateMode = imDefault); overload;
实现代码：
type
TInterpolateProc = procedure;
var
BicubicTable: Pointer;
BicubicSlope: Single;
BilinearTable: Pointer;
(*****************************************************************************
* typedef UINT ARGB *
* ARGB GetBilinearColor(int x(*256), int y(*256), void* Scan0, UINT Stride) *
* *
* int x0 = x / 256 *
* int y0 = y / 256 *
* BYTE *pScan0 = Scan0 + y0 * Stride + y0 * 4 *
* BYTE c[4][4] *
* c[0] = *pScan0 // (x0, y0) *
* c[1] = *(pScan0 + Stride) // (x0, y0+1) *
* c[2] = *(pScan0 + 4) // (x0+1, y0) *
* c[3] = *(PScan0 + Stride + 4) // (x0+1, y0+1) *
* int u = x & 0xff *
* int v = y & 0xff *
* int m0 = (255-v) * (255-u) *
* int m1 = v * (255-u) *
* int m2 = (255-v) * u *
* int m3 = v * u *
* BYTE ARGB[4] *
* for (int i = 0; i < 4; i ++) *
* ARGB[i] = (c[0][i]*m0 + c[1][i]*m1 + c[2][i]*m2 + c[3][i]*m3) / 65536 *
*****************************************************************************)
procedure GetBilinearColor;
asm
and edx, 255
and ecx, 255
shl edx, 4
shl ecx, 4
mov eax, BilinearTable
movq mm0, [esi] // mm0 = C2 (x0+1, y0) C0(x0, y0)
movq mm1, mm0
add esi, [ebx].TImageData.Stride
// [esi] = C3(x0+1, y0+1) C1(x0, y0+1)
punpcklbw mm0, [esi] // mm0 = A1 A0 R1 R0 G1 G0 B1 B0
punpckhbw mm1, [esi] // mm1 = A3 A2 R3 R2 G3 G2 B3 B2
movq mm2, mm0
movq mm3, mm1
punpcklbw mm0, mm7 // mm0 = 00 G1 00 G0 00 B1 00 B0
punpcklbw mm1, mm7 // mm1 = 00 G3 00 G2 00 B3 00 B2
punpckhbw mm2, mm7 // mm2 = 00 A1 00 A0 00 R1 00 R0
punpckhbw mm3, mm7 // mm3 = 00 A3 00 A2 00 R3 00 R2
movq mm4, [eax + edx]
pmullw mm4, [eax + ecx + 8]
psrlw mm4, 1 // 先除以2，否则后面的word有符号乘法会扩展符号位
movq mm5, mm4
punpckldq mm4, mm4 // mm4 = 00 m1 00 m0 00 m1 00 m0
punpckhdq mm5, mm5 // mm5 = 00 m3 00 m2 00 m3 00 m2
pmaddwd mm0, mm4 // mm0 = G1*m1+G0*m0 B1*m1+B0*m0
pmaddwd mm1, mm5 // mm1 = G3*m3+G2*m2 B3*m3+B2*m2
pmaddwd mm2, mm4 // mm2 = A1*m1+A0*m0 R1*m1+R0*m0
pmaddwd mm3, mm5 // mm3 = A3*m3+A2*m2 R3*m3+R2*m2
paddd mm0, mm1 // mm0 = G3n+G2n+G1n+G0n B3n+B2n+B1n+B0n
paddd mm2, mm3 // mm2 = A2n+A2n+A1n+A0n R3n+R2n+R1n+R0n
psrld mm0, 15 // mm0 = Gn/0x8000 Bn/0x8000
psrld mm2, 15 // mm2 = An/0x8000 Rn/0x8000
packssdw mm0, mm2 // mm0 = 00 An 00 Rn 00 Gn 00 Bn
packuswb mm0, mm0 // mm0 = An Rn Gn Bn An Rn Gn Bn
end;
procedure GetNearColor;
asm
movd mm0, [esi]
end;
procedure GetBicubicColor;
procedure SumBicubic;
asm
movd mm1, [esi]
movd mm2, [esi + 4]
movd mm3, [esi + 8]
movd mm4, [esi + 12]
punpcklbw mm1, mm7
punpcklbw mm2, mm7
punpcklbw mm3, mm7
punpcklbw mm4, mm7
psllw mm1, 7
psllw mm2, 7
psllw mm3, 7
psllw mm4, 7
pmulhw mm1, [edi + 256 * 8 + edx]
pmulhw mm2, [edi + edx]
pmulhw mm3, [edi + 256 * 8 + eax]
pmulhw mm4, [edi + 512 * 8 + eax]
paddsw mm1, mm2
paddsw mm3, mm4
paddsw mm1, mm3
pmulhw mm1, mm5
paddsw mm0, mm1
add esi, [ebx].TImageData.Stride
end;
asm
push edi
mov edi, BicubicTable// edi = int64 uvTable (item * 16384)
and edx, 255 // u = x & 255
shl edx, 3 // edx = u * 8
mov eax, edx // eax = -edx
neg eax
and ecx, 255 // v = y & 255
shl ecx, 3 // ecx = v * 8
pxor mm0, mm0
movq mm5, [edi + 256 * 8 + ecx]
call SumBicubic
movq mm5, [edi + ecx]
call SumBicubic
neg ecx
movq mm5, [edi + 256 * 8 + ecx]
call SumBicubic
movq mm5, [edi + 512 * 8 + ecx]
call SumBicubic
paddw mm0, mm6 // argb += 4
psraw mm0, 3 // argb /= 8
packuswb mm0, mm0
pop edi
end;
procedure AlphaBlendPixel;
asm
// movd mm0, eax // mm0 = 00 00 00 00 As Rs Gs Bs
movd mm1, [edi] // mm1 = 00 00 00 00 Ad Rd Gd Bd
punpcklbw mm0, mm7 // mm0 = 00 As 00 Rs 00 Gs 00 Bs
punpcklbw mm1, mm7 // mm1 = 00 Ad 00 Rd 00 Gd 00 Bd
movq mm2, mm0
punpckhwd mm2, mm2
punpckhdq mm2, mm2 // mm2 = Alpha Alpha Alpha Alpha
psubw mm0, mm1 // mm0 = As-Ad Rs-Rd Gs-Gd Bs-Bd
pmullw mm0, mm2 // mm0 = As*Alpha Rs*Alpha Gs*Alpha Bs*Alpha
psllw mm1, 8 // mm1 = Ad*256 Rd*256 Gd*256 Bd*256
paddw mm0, mm1 // mm0 = 00 An 00 Rn 00 Gn 00 Bn
psrlw mm0, 8 // mm0 = An/256 Rn/256 Gn/256 Bn/256
packuswb mm0, mm7 // mm0 = 00 00 00 00 An Rn Gn Bn
movd [edi], mm0
end;
function GetInterpolateProc(IpMode: TInterpolateMode; var Proc: TInterpolateProc): Integer;
begin
case IpMode of
imNear:
begin
Result := 1;
Proc := GetNearColor;
end;
imBicubic:
begin
Result := 4;
Proc := GetBicubicColor;
end
else
begin
Result := 2;
Proc := GetBilinearColor;
end;
end;
end;
procedure ImageScale(Dest: TImageData; const Source: TImageData; IpMode: TInterpolateMode);
var
x, y: Integer;
Width, Height: Integer;
xDelta, yDelta: Integer;
Radius, dstOffset: Integer;
src: TImageData;
GetColor: TInterpolateProc;
procedure DoScale(dst: TImageData);
asm
pxor mm7, mm7
mov edx, 04040404h
movd mm6, edx
punpcklbw mm6, mm7
lea edx, src
push edx
call SetDataCopyReg
imul ecx, xDelta
imul edx, yDelta
add ecx, x
add edx, y
mov Width, ecx
mov Height, edx
mov dstOffset, ebx
pop ebx
mov ecx, y // for (; y < Height; y ++){
@yLoop: // {
mov esi, ecx
sar esi, 8 // esi = Source.Scan0 + y / 256 * Source.Stride
imul esi, [ebx].TImageData.Stride
add esi, [ebx].TImageData.Scan0
mov edx, x // for (; x < Width; x ++){
@xLoop: // {
push esi
push edx
push ecx
mov eax, edx
sar eax, 8
shl eax, 2
add esi, eax // esi += (x / 256 * 4)
call GetColor // mm0 = GetColor(src, esi, x, y)
call AlphaBlendPixel // AlphaBlendPixel(mm0, edi)
add edi, 4 // edi += 4
pop ecx
pop edx
pop esi
add edx, xDelta // x0 += xDelta
cmp edx, Width
jl @xLoop // }
add edi, dstOffset // edi += dstOffset
add ecx, yDelta // y0 += yDelta
cmp ecx, Height
jl @yLoop // }
emms
end;
begin
Radius := GetInterpolateProc(IpMode, GetColor);
xDelta := (Source.Width shl 8) div Dest.Width;
yDelta := (Source.Height shl 8) div Dest.Height;
x := (xDelta{ shr 1}) + (Radius shl 7);
y := (yDelta{ shr 1}) + (Radius shl 7);
src := ImageGetExpandData(Source, 0, 0, Source.Width, Source.Height, Radius);
try
DoScale(Dest);
finally
FreeImageData(src);
end;
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TImageData; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src, dst: TImageData;
begin
if not ((ScaleX > 0.0) and (ScaleY > 0.0)) then
Exit;
dst := GetSubImageData(Dest, x, y, Round(Source.Width * ScaleX),
Round(Source.Height * ScaleY));
if ImageEmpty(dst) then Exit;
if x < 0 then x := -Trunc(x / ScaleX) else x := 0;
if y < 0 then y := -Trunc(y / ScaleY) else y := 0;
src := GetSubImageData(Source, x, y, Round(dst.Width / ScaleX),
Round(dst.Height / ScaleY));
ImageScale(dst, src, IpMode);
end;
procedure ImageScale(Dest: TImageData; const Source: TGraphic;
IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, src, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGraphic; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, x, y, src, ScaleX, ScaleY, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData;
const Source: TGpBitmap; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, src, IpMode);
FreeImageData(src);
end;
procedure ImageScale(Dest: TImageData; x, y: Integer;
const Source: TGpBitmap; ScaleX, ScaleY: Single; IpMode: TInterpolateMode);
var
src: TImageData;
begin
src := GetImageData(Source);
ImageScale(Dest, x, y, src, ScaleX, ScaleY, IpMode);
FreeImageData(src);
end;
procedure SetBicubicSlope(const Value: Single);
type
TBicArray = array[0..3] of Smallint;
PBicArray = ^TBicArray;
var
I: Integer;
P: PBicArray;
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0.0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1.0 then
Result := (Value + 2.0) * x3 - (Value + 3.0) * x2 + 1.0
else if x <= 2.0 then
Result := Value * x3 - (5.0 * Value) * x2 + (8.0 * Value) * x - (4.0 * Value)
else Result := 0.0;
end;
begin
if (BicubicSlope <> Value) and (Value < 0.0) {and (Value >= -2.0)} then
begin
BicubicSlope := Value;
P := BicubicTable;
for I := 0 to 512 do
begin
P^[0] := Round(16384 * BicubicFunc(I * (1.0 / 256)));
P^[1] := P^[0];
P^[2] := P^[0];
P^[3] := P^[0];
Inc(P);
end;
end;
end;
临近插值过程很简单，就一句代码，而线性插值过程和双立方插值过程则较复杂，而且对于各像素的插值比例计算更是耗时，为了加快插值速度，线性插值过程和双立方插值过程都用了事先计算好的插值比例表，分别存放在BilinearTable变量和BicubicTable变量中，这2个变量的初始化是在单元的初始化代码中实现的：
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procedure InitBilinearTable;
begin
BilinearTable := GlobalAllocPtr(GMEM_MOVEABLE, 256 * 2 * 8);
asm
push esi
mov esi, BilinearTable
xor ecx, ecx
@SumLoop:
mov edx, ecx
and edx, 255 // u(v) = x & 0xff
mov eax, 100h
sub eax, edx
jnz @@1
dec edx
jmp @@2
@@1:
test edx, edx
jnz @@2
dec eax
@@2:
shl edx, 16
or edx, eax // edx = 00 u(v) 00 ff-u(v)
movd mm0, edx
movd mm1, edx
punpcklwd mm0, mm0 // mm0 = 00 u 00 u 00 ff-u 00 ff-u
punpckldq mm1, mm1 // mm1 = 00 v 00 ff-v 00 v 00 ff-v
movq [esi], mm0
movq [esi + 8], mm1
add esi, 16
inc ecx
cmp ecx, 256
jl @SumLoop
emms
pop esi
end;
end;
initialization
begin
InitBilinearTable;
BicubicTable := GlobalAllocPtr(GMEM_MOVEABLE, (512 + 1) * 8);
SetBicubicSlope(-0.75);
end;
finalization
begin
GlobalFreePtr(BicubicTable);
GlobalFreePtr(BilinearTable);
end;
procedure InitBilinearTable;
begin
BilinearTable := GlobalAllocPtr(GMEM_MOVEABLE, 256 * 2 * 8);
asm
push esi
mov esi, BilinearTable
xor ecx, ecx
@SumLoop:
mov edx, ecx
and edx, 255 // u(v) = x & 0xff
mov eax, 100h
sub eax, edx
jnz @@1
dec edx
jmp @@2
@@1:
test edx, edx
jnz @@2
dec eax
@@2:
shl edx, 16
or edx, eax // edx = 00 u(v) 00 ff-u(v)
movd mm0, edx
movd mm1, edx
punpcklwd mm0, mm0 // mm0 = 00 u 00 u 00 ff-u 00 ff-u
punpckldq mm1, mm1 // mm1 = 00 v 00 ff-v 00 v 00 ff-v
movq [esi], mm0
movq [esi + 8], mm1
add esi, 16
inc ecx
cmp ecx, 256
jl @SumLoop
emms
pop esi
end;
end;
initialization
begin
InitBilinearTable;
BicubicTable := GlobalAllocPtr(GMEM_MOVEABLE, (512 + 1) * 8);
SetBicubicSlope(-0.75);
end;
finalization
begin
GlobalFreePtr(BicubicTable);
GlobalFreePtr(BilinearTable);
end;
其中，通过调用SetBicubicSlope可改变双立方插值的效果，这个值一般在-0.5 -- -2.0之间，初始值为-0.75。
图像旋转过程也要用到上面的插值过程的。
关于线性插值原理，在GetBilinearColor过程前面有一段伪代码作为解释；为了帮助理解双立方插值方式，下面给出其纯Pascal的浮点版和整数版代码：
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type
TImageData = packed record
Width: LongWord; // 图像宽度
Height: LongWord; // 图像高度
Stride: LongWord; // 图像扫描线字节长度
Scan0: Pointer; // 图像数据地址
end;
// 浮点数版，Source四周的边界分别扩展了3
procedure BicubicScale(Source, Dest: TImageData);
const A = -0.75; // 0.0 < BicuBicSlope <= 2.0
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1 then
Result := (A + 2) * x3 - (A + 3) * x2 + 1
else if x <= 2 then
Result := A * x3 - (5 * A) * x2 + (8 * A) * x - (4 * A)
else Result := 0;
end;
function Bicubic(fx, fy: double): TRGBQuad;
var
x, y, x0, y0: Integer;
fu, fv: double;
pixel: array[0..3, 0..3] of PRGBQuad;
afu, afv, aARGB, sARGB: array[0..3] of double;
i, j: Integer;
begin
x0 := Trunc(floor(fx));
y0 := Trunc(floor(fy));
fu := fx - x0;
fv := fy - y0;
for i := 0 to 3 do
begin
for j := 0 to 3 do
begin
x := x0 - 1 + j;
y := y0 - 1 + i;
pixel[i, j] := PRGBQuad(LongWord(Source.Scan0) + y * Source.Stride + x shl 2);
end;
sARGB[i] := 0;
end;
afu[0] := BicubicFunc(1 + fu);
afu[1] := BicubicFunc(fu);
afu[2] := BicubicFunc(1 - fu);
afu[3] := BicubicFunc(2 - fu);
afv[0] := BicubicFunc(1 + fv);
afv[1] := BicubicFunc(fv);
afv[2] := BicubicFunc(1 - fv);
afv[3] := BicubicFunc(2 - fv);
for i := 0 to 3 do
begin
for j := 0 to 3 do
aARGB[j] := 0;
for j := 0 to 3 do
begin
aARGB[3] := aARGB[3] + afu[j] * pixel[i, j]^.rgbReserved;
aARGB[2] := aARGB[2] + afu[j] * pixel[i, j]^.rgbRed;
aARGB[1] := aARGB[1] + afu[j] * pixel[i, j]^.rgbGreen;
aARGB[0] := aARGB[0] + afu[j] * pixel[i, j]^.rgbBlue;
end;
sARGB[3] := sARGB[3] + aARGB[3] * afv[i];
sARGB[2] := sARGB[2] + aARGB[2] * afv[i];
sARGB[1] := sARGB[1] + aARGB[1] * afv[i];
sARGB[0] := sARGB[0] + aARGB[0] * afv[i];
end;
Result.rgbBlue := Max(0, Min(255, Round(sARGB[0])));
Result.rgbGreen := Max(0, Min(255, Round(sARGB[1])));
Result.rgbRed := Max(0, Min(255, Round(sARGB[2])));
Result.rgbReserved := Max(0, Min(255, Round(sARGB[3])));
end;
var
x, y: Integer;
fx, fy: double;
Offset: LongWord;
p: PLongWord;//PRGBQuad;
begin
Offset := Dest.Stride - Dest.Width shl 2;
p := PLongWord(Dest.Scan0);
for y := 0 to Dest.Height - 1 do
begin
fy := (y + 0.4999999) * Source.Height / Dest.Height - 0.5;
for x := 0 to Dest.Width - 1 do
begin
fx := (x + 0.4999999) * Source.Width / Dest.Width - 0.5;
P^ := LongWord(Bicubic(fx, fy));
Inc(p);
end;
Inc(LongWord(p), Offset);
end;
end;
const InterpolationRadius = 3;
var
BicubicUVTable: array[0..512] of Integer;
procedure InitBicubicUVTable;
const A = -0.75;
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1 then
Result := (A + 2) * x3 - (A + 3) * x2 + 1
else if x <= 2 then
Result := A * x3 - (5 * A) * x2 + (8 * A) * x - (4 * A)
else Result := 0;
end;
var
I: Integer;
begin
for I := 0 to 512 do
BicubicUVTable[I] := Round(256 * BicubicFunc(I * (1.0 / 256)));
end;
// 定点数版，Source四周的边界分别扩展了3
procedure BicubicScale(Source, Dest: TImageData);
function Bicubic(x, y: Integer): TRGBQuad;
var
x0, y0, u, v: Integer;
pixel: PRGBQuad;
au, av, aARGB, sARGB: array[0..3] of Integer;
i, j: Integer;
begin
u := x and 255;
v := y and 255;
pixel := PRGBQuad(LongWord(Source.Scan0) + (y div 256 - 1) * Source.Stride + ((x div 256 - 1) shl 2));
for i := 0 to 3 do
sARGB[i] := 0;
au[0] := BicubicUVTable[256 + u];
au[1] := BicubicUVTable[u];
au[2] := BicubicUVTable[256 - u];
au[3] := BicubicUVTable[512 - u];
av[0] := BicubicUVTable[256 + v];
av[1] := BicubicUVTable[v];
av[2] := BicubicUVTable[256 - v];
av[3] := BicubicUVTable[512 - v];
for i := 0 to 3 do
begin
for j := 0 to 3 do
aARGB[j] := 0;
for j := 0 to 3 do
begin
aARGB[3] := aARGB[3] + au[j] * pixel^.rgbReserved;
aARGB[2] := aARGB[2] + au[j] * pixel^.rgbRed;
aARGB[1] := aARGB[1] + au[j] * pixel^.rgbGreen;
aARGB[0] := aARGB[0] + au[j] * pixel^.rgbBlue;
Inc(LongWord(pixel), 4);
end;
sARGB[3] := sARGB[3] + aARGB[3] * av[i];
sARGB[2] := sARGB[2] + aARGB[2] * av[i];
sARGB[1] := sARGB[1] + aARGB[1] * av[i];
sARGB[0] := sARGB[0] + aARGB[0] * av[i];
Inc(LongWord(pixel), FStride - 16);
end;
Result.rgbBlue := Max(0, Min(255, sARGB[0] div 65536));
Result.rgbGreen := Max(0, Min(255, sARGB[1] div 65536));
Result.rgbRed := Max(0, Min(255, sARGB[2] div 65536));
Result.rgbReserved := Max(0, Min(255, sARGB[3] div 65536));
end;
var
x, x0, y, xDelta, yDelta: Integer;
w, h: Integer;
Offset: LongWord;
p: PLongWord;
begin
InitBicubicUVTable;
p := PLongWord(Dest.Scan0);
Offset := Dest.Stride - Dest.Width shl 2;
yDelta := ((Source.Height - InterpolationRadius * 2) * 256) div Dest.Height;
xDelta := ((Source.Width - InterpolationRadius * 2) * 256) div Dest.Width;
y := (yDelta shr 1) - $80 + $200;
x0 := (xDelta shr 1) - $80 + $200;
h := Dest.Height * yDelta + y;
w := Dest.Width * xDelta + x0;
while y < h do
begin
x := x0;
while x < w do
begin
P^ := LongWord(Bicubic(x, y));
Inc(x, xDelta);
Inc(p);
end;
Inc(y, yDelta);
Inc(LongWord(p), Offset);
end;
end;
type
TImageData = packed record
Width: LongWord; // 图像宽度
Height: LongWord; // 图像高度
Stride: LongWord; // 图像扫描线字节长度
Scan0: Pointer; // 图像数据地址
end;
// 浮点数版，Source四周的边界分别扩展了3
procedure BicubicScale(Source, Dest: TImageData);
const A = -0.75; // 0.0 < BicuBicSlope <= 2.0
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1 then
Result := (A + 2) * x3 - (A + 3) * x2 + 1
else if x <= 2 then
Result := A * x3 - (5 * A) * x2 + (8 * A) * x - (4 * A)
else Result := 0;
end;
function Bicubic(fx, fy: double): TRGBQuad;
var
x, y, x0, y0: Integer;
fu, fv: double;
pixel: array[0..3, 0..3] of PRGBQuad;
afu, afv, aARGB, sARGB: array[0..3] of double;
i, j: Integer;
begin
x0 := Trunc(floor(fx));
y0 := Trunc(floor(fy));
fu := fx - x0;
fv := fy - y0;
for i := 0 to 3 do
begin
for j := 0 to 3 do
begin
x := x0 - 1 + j;
y := y0 - 1 + i;
pixel[i, j] := PRGBQuad(LongWord(Source.Scan0) + y * Source.Stride + x shl 2);
end;
sARGB[i] := 0;
end;
afu[0] := BicubicFunc(1 + fu);
afu[1] := BicubicFunc(fu);
afu[2] := BicubicFunc(1 - fu);
afu[3] := BicubicFunc(2 - fu);
afv[0] := BicubicFunc(1 + fv);
afv[1] := BicubicFunc(fv);
afv[2] := BicubicFunc(1 - fv);
afv[3] := BicubicFunc(2 - fv);
for i := 0 to 3 do
begin
for j := 0 to 3 do
aARGB[j] := 0;
for j := 0 to 3 do
begin
aARGB[3] := aARGB[3] + afu[j] * pixel[i, j]^.rgbReserved;
aARGB[2] := aARGB[2] + afu[j] * pixel[i, j]^.rgbRed;
aARGB[1] := aARGB[1] + afu[j] * pixel[i, j]^.rgbGreen;
aARGB[0] := aARGB[0] + afu[j] * pixel[i, j]^.rgbBlue;
end;
sARGB[3] := sARGB[3] + aARGB[3] * afv[i];
sARGB[2] := sARGB[2] + aARGB[2] * afv[i];
sARGB[1] := sARGB[1] + aARGB[1] * afv[i];
sARGB[0] := sARGB[0] + aARGB[0] * afv[i];
end;
Result.rgbBlue := Max(0, Min(255, Round(sARGB[0])));
Result.rgbGreen := Max(0, Min(255, Round(sARGB[1])));
Result.rgbRed := Max(0, Min(255, Round(sARGB[2])));
Result.rgbReserved := Max(0, Min(255, Round(sARGB[3])));
end;
var
x, y: Integer;
fx, fy: double;
Offset: LongWord;
p: PLongWord;//PRGBQuad;
begin
Offset := Dest.Stride - Dest.Width shl 2;
p := PLongWord(Dest.Scan0);
for y := 0 to Dest.Height - 1 do
begin
fy := (y + 0.4999999) * Source.Height / Dest.Height - 0.5;
for x := 0 to Dest.Width - 1 do
begin
fx := (x + 0.4999999) * Source.Width / Dest.Width - 0.5;
P^ := LongWord(Bicubic(fx, fy));
Inc(p);
end;
Inc(LongWord(p), Offset);
end;
end;
const InterpolationRadius = 3;
var
BicubicUVTable: array[0..512] of Integer;
procedure InitBicubicUVTable;
const A = -0.75;
function BicubicFunc(x : double): double;
var
x2, x3: double;
begin
if x < 0 then x := -x;
x2 := x * x;
x3 := x2 * x;
if x <= 1 then
Result := (A + 2) * x3 - (A + 3) * x2 + 1
else if x <= 2 then
Result := A * x3 - (5 * A) * x2 + (8 * A) * x - (4 * A)
else Result := 0;
end;
var
I: Integer;
begin
for I := 0 to 512 do
BicubicUVTable[I] := Round(256 * BicubicFunc(I * (1.0 / 256)));
end;
// 定点数版，Source四周的边界分别扩展了3
procedure BicubicScale(Source, Dest: TImageData);
function Bicubic(x, y: Integer): TRGBQuad;
var
x0, y0, u, v: Integer;
pixel: PRGBQuad;
au, av, aARGB, sARGB: array[0..3] of Integer;
i, j: Integer;
begin
u := x and 255;
v := y and 255;
pixel := PRGBQuad(LongWord(Source.Scan0) + (y div 256 - 1) * Source.Stride + ((x div 256 - 1) shl 2));
for i := 0 to 3 do
sARGB[i] := 0;
au[0] := BicubicUVTable[256 + u];
au[1] := BicubicUVTable[u];
au[2] := BicubicUVTable[256 - u];
au[3] := BicubicUVTable[512 - u];
av[0] := BicubicUVTable[256 + v];
av[1] := BicubicUVTable[v];
av[2] := BicubicUVTable[256 - v];
av[3] := BicubicUVTable[512 - v];
for i := 0 to 3 do
begin
for j := 0 to 3 do
aARGB[j] := 0;
for j := 0 to 3 do
begin
aARGB[3] := aARGB[3] + au[j] * pixel^.rgbReserved;
aARGB[2] := aARGB[2] + au[j] * pixel^.rgbRed;
aARGB[1] := aARGB[1] + au[j] * pixel^.rgbGreen;
aARGB[0] := aARGB[0] + au[j] * pixel^.rgbBlue;
Inc(LongWord(pixel), 4);
end;
sARGB[3] := sARGB[3] + aARGB[3] * av[i];
sARGB[2] := sARGB[2] + aARGB[2] * av[i];
sARGB[1] := sARGB[1] + aARGB[1] * av[i];
sARGB[0] := sARGB[0] + aARGB[0] * av[i];
Inc(LongWord(pixel), FStride - 16);
end;
Result.rgbBlue := Max(0, Min(255, sARGB[0] div 65536));
Result.rgbGreen := Max(0, Min(255, sARGB[1] div 65536));
Result.rgbRed := Max(0, Min(255, sARGB[2] div 65536));
Result.rgbReserved := Max(0, Min(255, sARGB[3] div 65536));
end;
var
x, x0, y, xDelta, yDelta: Integer;
w, h: Integer;
Offset: LongWord;
p: PLongWord;
begin
InitBicubicUVTable;
p := PLongWord(Dest.Scan0);
Offset := Dest.Stride - Dest.Width shl 2;
yDelta := ((Source.Height - InterpolationRadius * 2) * 256) div Dest.Height;
xDelta := ((Source.Width - InterpolationRadius * 2) * 256) div Dest.Width;
y := (yDelta shr 1) - $80 + $200;
x0 := (xDelta shr 1) - $80 + $200;
h := Dest.Height * yDelta + y;
w := Dest.Width * xDelta + x0;
while y < h do
begin
x := x0;
while x < w do
begin
P^ := LongWord(Bicubic(x, y));
Inc(x, xDelta);
Inc(p);
end;
Inc(y, yDelta);
Inc(LongWord(p), Offset);
end;
end;
另外，有关插值边界的处理，一般有2种办法，一是在插值过程中进行判断坐标是否超界而作相应的处理，二是舍弃边界部分，对于后者我是不主张的，因为那样是不完整的处理。我采用了扩展边框的办法进行边框插值处理，这样一来，虽然多了一道拷贝过程，却少了具体插值过程的坐标判断，二者抵消，插值速度应该是差不多的（据我测试，扩展边框办法在图像放大和旋转处理中速度还是略快一些），但是简化了插值代码。
下面是一个简单的图像缩放例子：
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type
TMainForm = class(TForm)
Image1: TImage;
RadioButton1: TRadioButton;
RadioButton2: TRadioButton;
RadioButton3: TRadioButton;
Button1: TButton;
Image2: TImage;
procedure FormCreate(Sender: TObject);
procedure RadioButton1Click(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
FMode: TInterpolateMode;
public
{ Public declarations }
end;
var
MainForm: TMainForm;
implementation
{$R *.dfm}
procedure TMainForm.FormCreate(Sender: TObject);
begin
Image1.Picture.Bitmap.PixelFormat := pf24Bit;
RadioButton2.Checked := True;
RadioButton1Click(RadioButton2);
end;
procedure TMainForm.RadioButton1Click(Sender: TObject);
var
M: TInterpolateMode;
Data: TImageData;
begin
M := TInterpolateMode(TRadioButton(Sender).Tag);
if FMode <> M then
begin
FMode := M;
Data := NewImageData(Image1.Width, Image1.Height, 0);
ImageScale(Data, Image2.Picture.Graphic, FMode);
ImageDataAssignTo(Data, Image1.Picture.Bitmap);
FreeImageData(Data);
Image1.Invalidate;
end;
end;
procedure TMainForm.Button1Click(Sender: TObject);
begin
Close;
end;
type
TMainForm = class(TForm)
Image1: TImage;
RadioButton1: TRadioButton;
RadioButton2: TRadioButton;
RadioButton3: TRadioButton;
Button1: TButton;
Image2: TImage;
procedure FormCreate(Sender: TObject);
procedure RadioButton1Click(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
FMode: TInterpolateMode;
public
{ Public declarations }
end;
var
MainForm: TMainForm;
implementation
{$R *.dfm}
procedure TMainForm.FormCreate(Sender: TObject);
begin
Image1.Picture.Bitmap.PixelFormat := pf24Bit;
RadioButton2.Checked := True;
RadioButton1Click(RadioButton2);
end;
procedure TMainForm.RadioButton1Click(Sender: TObject);
var
M: TInterpolateMode;
Data: TImageData;
begin
M := TInterpolateMode(TRadioButton(Sender).Tag);
if FMode <> M then
begin
FMode := M;
Data := NewImageData(Image1.Width, Image1.Height, 0);
ImageScale(Data, Image2.Picture.Graphic, FMode);
ImageDataAssignTo(Data, Image1.Picture.Bitmap);
FreeImageData(Data);
Image1.Invalidate;
end;
end;
procedure TMainForm.Button1Click(Sender: TObject);
begin
Close;
end;
运行效果图如下：
文章中所用数据类型及一些过程见《Delphi图像处理 -- 数据类型及内部过程》和《Delphi图像处理 -- 图像像素结构与图像数据转换》。
