Draw a stretched and rotated image on TCanvas - delphi

i am trying to draw a rotated bitmap on a TImage canvas at some specified points, what i tried so far is i rotated the bitmap and then used stretched draw but i am not getting the results i want, the scenario goes like this
I map 4 points on a TImage canvas with mouse clicks and get its angle, the angle can be 0, 45, 90 anything, something like in the image i have attached
Now what i need is to draw another bitmap rotated and stretched on these points, i am having a hard time figuring this thing out
Regards

Many years ago, when stars was brighter and girls was younger, i wrote this code for unknown reason. It is VCL compatible, but can be adopter in order to be used in both VCL/FMX. It is simple class to draw arbitrary rectangle from bitmap to arbitrary rectangle at destination DC (so it could be bitmap or something else). It can paint destination picture with bilinear interpolation, then result looks not so ugly as with simple stretching. Maybe it can be useful for someone.
unit uBMPUtils;
interface
uses
windows, graphics, math, sysutils;
type
PIntegers = ^TIntegers;
TIntegers = array[0..high(integer) div sizeof(integer) - 16] of integer;
TDrawLine = procedure( pixelSize : integer;
var src;
srcLineAdd : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
var dst;
dstLen : integer) of object;
TDrawMode = (dmSimple, dmBilinear);
TBitmapDrawer = class
protected
tmp : TBitmap;
koefs : array[0..4096*4-1] of integer; // addr(Ux, Vy) = 4 * ( (trunc(Ux*16) << 6) + trunc(Vy*16) )
calculated : boolean;
DrawModeFlag : TDrawMode;
DrawLine : TDrawLine;
procedure precalculate; // precalculate koefs for fast bilinear interpolation
procedure drawLineSimple( pixelSize : integer;
var src;
srcLineAdd : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
var dst;
dstLen : integer);
procedure drawLineBilinear( pixelSize : integer;
var src;
srcLineAdd : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
var dst;
dstLen : integer);
procedure setDrawMode(m : TDrawMode);
public
constructor Create;
destructor Destroy; override;
procedure DrawTriangle(src : TBitmap; // source bitmap (pf24 or pf32!)
dst_dc : cardinal; // destination DC
dstRect : TRect; // limiting rect for output
A1, A2, A3, // arbitrary rectange at Src bitmap
B1, B2, B3 : TPoint); // arbitrary rectange at DST_DC device
procedure DrawRectangle(src : TBitmap; // source bitmap (pf24 or pf32!)
dst_dc : cardinal; // destination DC
dstRect : TRect; // limiting rect for output
A1, A2, A3, A4, // arbitrary rectange at Src bitmap
B1, B2, B3, B4 : TPoint); // arbitrary rectange at DST_DC device
property DrawMode: TDrawMode read DrawModeFlag write setDrawMode; // Default: dmBilinear
end;
implementation
function HorAtLine(var x : integer; y, x1,y1,x2,y2 : integer):boolean;
begin
if y1 = y2 then result := false else
begin
result := (y >= y1) and (y <= y2) or (y >= y2) and (y <= y1);
if result then x := x1 + (x2 - x1) * (y - y1) div (y2 - y1);
end;
end;
procedure LineProportion(var src_x, src_y : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
dst_x, dst_y : integer;
dst_x1, dst_y1, dst_x2, dst_y2 : integer);
begin
if abs(dst_x2 - dst_x1) > abs(dst_y2 - dst_y1) then begin // proportions form Y
src_x := src_x1 + (src_x2 - src_x1) * (dst_x - dst_x1) div (dst_x2 - dst_x1);
src_y := src_y1 + (src_y2 - src_y1) * (dst_x - dst_x1) div (dst_x2 - dst_x1);
end else begin
src_x := src_x1 + (src_x2 - src_x1) * (dst_y - dst_y1) div (dst_y2 - dst_y1);
src_y := src_y1 + (src_y2 - src_y1) * (dst_y - dst_y1) div (dst_y2 - dst_y1);
end;
end;
// ---------------------------------------------- TBitmapDrawer --------------------------------------------------------
procedure TBitmapDrawer.precalculate;
var
n, u, v : integer;
Uf, Vf, k1,k2,k3,k4 : double;
begin
calculated := true;
for V := 0 to 63 do
for U := 0 to 63 do
begin
Uf := U / 64;
Vf := V / 64;
k1 := (1 - Uf) * (1 - Vf);
k2 := Uf * (1 - Vf);
k3 := (1 - Uf) * Vf;
k4 := Uf * Vf;
n := ((U shl 6) + V) * 4;
koefs[n] := trunc(k1*65536);
koefs[n+1] := trunc(k2*65536);
koefs[n+2] := trunc(k3*65536);
koefs[n+3] := trunc(k4*65536);
end;
end;
constructor TBitmapDrawer.create;
begin
inherited create;
tmp := TBitmap.create;
tmp.Height := 1;
drawMode := dmBilinear;
precalculate;
end;
destructor TBitmapDrawer.Destroy;
begin
FreeandNil(tmp);
inherited;
end;
procedure TBitmapDrawer.DrawRectangle(src : TBitmap;
dst_dc : cardinal;
dstRect : TRect;
A1, A2, A3, A4,
B1, B2, B3, B4 : TPoint);
begin
DrawTriangle(src, dst_dc, dstRect, A1, A2, A3, B1, B2, B3);
DrawTriangle(src, dst_dc, dstRect, A1, A3, A4, B1, B3, B4);
end;
procedure TBitmapDrawer.DrawTriangle(src : TBitmap;
dst_dc : cardinal;
dstRect : TRect;
A1, A2, A3,
B1, B2, B3 : TPoint);
var
pixelSize, srcAdd, left_x, left_y, right_x, right_y: integer;
minx, maxx, x, y, top, bottom : integer;
pb : pointer;
begin
if src.height > 1 then srcAdd := integer(PAnsiChar(src.scanline[1]) - PAnsiChar(src.scanline[0])) else srcAdd := 0;
top := min(min(b1.y, b2.y), b3.y);
bottom := max(max(b1.y, b2.y), b3.y);
if (top > dstRect.Bottom) or (bottom < dstRect.Top) then exit;
if top < dstRect.Top then top := dstRect.Top;
if bottom > dstRect.Bottom then bottom := dstRect.Bottom;
case src.pixelFormat of
pf24bit : pixelsize := 3;
pf32bit : pixelsize := 4;
else raise exception.create('Error');
end;
if tmp.PixelFormat <> src.PixelFormat then tmp.PixelFormat := src.PixelFormat;
y := max(max(b1.X, b2.x), b3.x) - min(min(b1.X, b2.x), b3.x) + 1;
if (tmp.Width < y) then tmp.Width := y;
pb := tmp.scanline[0];
for y := top to bottom do // Y at destination picture
begin
minx := high(integer);
maxx := low(integer);
if HorAtLine(x,y, b1.X, b1.Y, b2.x, b2.Y) then
begin
if x < minx then begin
minx := x;
LineProportion(left_x, left_y, a1.X, a1.Y, a2.x, a2.Y, x,y, b1.X, b1.Y, b2.X, b2.Y);
end;
if x > maxx then begin
LineProportion(right_x, right_y, a1.X, a1.Y, a2.x, a2.Y, x,y, b1.X, b1.Y, b2.X, b2.Y);
maxx := x;
end;
end;
if HorAtLine(x,y, b2.X, b2.Y, b3.x, b3.Y) then
begin
if x < minx then begin
minx := x;
LineProportion(left_x, left_y, a2.X, a2.Y, a3.x, a3.Y, x,y, b2.X, b2.Y, b3.X, b3.Y);
end;
if x > maxx then begin
LineProportion(right_x, right_y, a2.X, a2.Y, a3.x, a3.Y, x,y, b2.X, b2.Y, b3.X, b3.Y);
maxx := x;
end;
end;
if HorAtLine(x,y, b3.X, b3.Y, b1.x, b1.Y) then
begin
if x < minx then begin
minx := x;
LineProportion(left_x, left_y, a3.X, a3.Y, a1.x, a1.Y, x,y, b3.X, b3.Y, b1.X, b1.Y);
end;
if x > maxx then begin
LineProportion(right_x, right_y, a3.X, a3.Y, a1.x, a1.Y, x,y, b3.X, b3.Y, b1.X, b1.Y);
maxx := x;
end;
end;
if minx > maxx then continue;
// destination line (minx, y) - (maxx, y) - now we can find it at source picture
drawLine(pixelSize, src.ScanLine[0]^, srcAdd, left_x, left_y, right_x, right_y, pb^, maxx - minx + 1);
bitblt(dst_dc, minx, y, maxx-minx+1, 1, tmp.Canvas.Handle, 0,0, srccopy);
end;
end;
procedure TBitmapDrawer.drawLineSimple( pixelSize : integer;
var src;
srcLineAdd : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
var dst;
dstLen : integer);
var
dst_ptr : PAnsiChar;
i, px, py : integer;
begin
dst_ptr := #dst;
px := (src_x2 - src_x1) * 65536 div dstLen;
py := (src_y2 - src_y1) * 65536 div dstLen;
src_x1 := src_x1 * 65536;
src_y1 := src_y1 * 65536;
for i := 0 to dstLen - 1 do
begin
pinteger(dst_ptr)^ := pinteger( PAnsiChar(#src) +
((src_y1 + i * py) shr 16) * srcLineAdd +
((src_x1 + i * px) shr 16) * pixelSize
)^;
inc(dst_ptr, pixelSize);
end;
end;
procedure TBitmapDrawer.drawLineBilinear( pixelSize : integer;
var src;
srcLineAdd : integer;
src_x1, src_y1, src_x2, src_y2 : integer;
var dst;
dstLen : integer);
var
src_ptr, dst_ptr : PAnsiChar;
u,v,Uf,Vf : integer;
i : integer;
k : PIntegers;
c1,c2,c3,c4 : TColor;
begin
dst_ptr := #dst;
for i := 0 to dstLen - 1 do
begin
u := src_x1 + i * (src_x2 - src_x1) div dstLen;
v := src_y1 + i * (src_y2 - src_y1) div dstLen;
Uf := (src_x1 + i * (src_x2 - src_x1) * 64 div dstLen) and $3f;
Vf := (src_y1 + i * (src_y2 - src_y1) * 64 div dstLen) and $3f;
k := #koefs[4*((Uf shl 6) + Vf)];
src_ptr := PAnsiChar(#src) + v * srcLineAdd + u * pixelSize;
c1 := pinteger(src_ptr)^;
c2 := pinteger(src_ptr + 4)^;
c3 := pinteger(src_ptr + srcLineAdd)^;
c4 := pinteger(src_ptr + srcLineAdd + 4)^;
pinteger(dst_ptr)^ :=
( (c1 and $FF)*k[0] shr 16 +
(c2 and $FF)*k[1] shr 16 +
(c3 and $FF)*k[2] shr 16 +
(c4 and $FF)*k[3] shr 16 )
or
( ((c1 shr 8) and $FF)*k[0] shr 16 +
((c2 shr 8) and $FF)*k[1] shr 16 +
((c3 shr 8) and $FF)*k[2] shr 16 +
((c4 shr 8) and $FF)*k[3] shr 16 ) shl 8
or
( ((c1 shr 16) and $FF)*k[0] shr 16 +
((c2 shr 16) and $FF)*k[1] shr 16 +
((c3 shr 16) and $FF)*k[2] shr 16 +
((c4 shr 16) and $FF)*k[3] shr 16 ) shl 16
or $02000000;
inc(dst_ptr, pixelSize);
end;
end;
procedure TBitmapDrawer.setDrawMode(m: TDrawMode);
begin
drawModeFlag := m;
case drawModeFlag of
dmSimple : drawLine := drawLineSimple;
dmBilinear : drawLine := drawLineBilinear;
end;
end;
end.

I finally got the desired output using Projective transformation method in Graphics32 http://graphics32.org/wiki/

Related

Is Delphi's Skewness correct

In Delphi one can calculate Skewness using System.Math's function MomentSkewKurtosis().
var m1, m2, m3, m4, skew, k: Extended;
System.Math.MomentSkewKurtosis([1.1,
3.345,
12.234,
11.945,
14.235,
16.876,
20.213,
11.001,
7.098,
21.234], m1, m2, m3, m4, skew, k);
This will prints skew equal to -0.200371489809269.
Minitab prints the value -0.24
SigmaXL prints the value -0.23611
The reason is that Delphi does not not perform adjustment.
Here is my implementation which calculates adjustment:
function Skewness(const X: array of Extended; const Adjusted: Boolean): Extended;
begin
var AMean := Mean(X);
var xi_minus_mean_power_3 := 0.0;
var xi_minus_mean_power_2 := 0.0;
for var i := Low(X) to High(X) do
begin
xi_minus_mean_power_3 := xi_minus_mean_power_3 + IntPower((X[i] - AMean), 3);
xi_minus_mean_power_2 := xi_minus_mean_power_2 + IntPower((X[i] - AMean), 2);
end;
// URL : https://www.gnu.org/software/octave/doc/v4.0.1/Descriptive-Statistics.html
{ mean ((x - mean (x)).^3)
skewness (X) = ------------------------.
std (x).^3
}
var N := Length(X);
Result := xi_minus_mean_power_3 / N /
IntPower(Sqrt(1 / N * xi_minus_mean_power_2), 3);
// URL : https://www.gnu.org/software/octave/doc/v4.0.1/Descriptive-Statistics.html
{ sqrt (N*(N-1)) mean ((x - mean (x)).^3)
skewness (X, 0) = -------------- * ------------------------.
(N - 2) std (x).^3
}
if Adjusted then
Result := Result * Sqrt(N * Pred(N)) / (N - 2);
end;
The helper routine IntPower is as follows:
function IntPower(const X: Extended; const N: Integer): Extended;
/// <remarks>
/// Calculate any float to non-negative integer power. Developed by Rory Daulton and used with permission. Last modified December 1998.
/// </remarks>
function IntPow(const Base: Extended; const Exponent: LongWord): Extended;
{ Heart of Rory Daulton's IntPower: assumes valid parameters &
non-negative exponent }
{$IFDEF WIN32}
asm
fld1 // Result := 1
cmp eax, 0 // eax := Exponent
jz ##3
fld Base
jmp ##2
##1: fmul ST, ST // X := Base * Base
##2: shr eax,1
jnc ##1
fmul ST(1),ST // Result := Result * X
jnz ##1
fstp st // pop X from FPU stack
##3:
fwait
end;
{$ENDIF}
{$IFDEF WIN64}
begin
Result := Power(Base, Exponent);
end;
{$ENDIF}
begin
if N = 0 then
Result := 1
else if (X = 0) then
begin
if N < 0 then
raise EMathError.Create('Zero cannot be raised to a negative power.')
else
Result := 0
end
else if (X = 1) then
Result := 1
else if X = -1 then
begin
if Odd (N) then
Result := -1
else
Result := 1
end
else if N > 0 then
Result := IntPow (X, N)
else
begin
var P: LongWord;
if N <> Low (LongInt) then
P := Abs(N)
else
P := LongWord(High(LongInt)) + 1;
try
Result := IntPow(X, P);
except
on EMathError do
begin
Result := IntPow(1 / X, P); // try again with another method, perhaps less precise
Exit;
end;
end;
Result := 1 / Result;
end;
end;
With that function the adjusted skewness becomes the accurate -0.237611357234441 matching Matlab and Minitab.
The only explanation I found is:
https://octave.org/doc/v4.0.1/Descriptive-Statistics.html
"The adjusted skewness coefficient is obtained by replacing the sample
second and third central moments by their bias-corrected versions."
Same goes with Kurtosis:
function Kurtosis(const X: array of Extended; const Adjusted: Boolean): Extended;
begin
var AMean := Mean(X);
var xi_minus_mean_power_4 := 0.0;
var xi_minus_mean_power_2 := 0.0;
for var i := Low(X) to High(X) do
begin
xi_minus_mean_power_4 := xi_minus_mean_power_4 + IntPower((X[i] - AMean), 4);
xi_minus_mean_power_2 := xi_minus_mean_power_2 + IntPower((X[i] - AMean), 2);
end;
{ mean ((x - mean (x)).^4)
k1 = ------------------------
std (x).^4
}
var N := Length(X);
Result := xi_minus_mean_power_4 / N /
IntPower(1 / N * xi_minus_mean_power_2, 2);
{ N - 1
k0 = 3 + -------------- * ((N + 1) * k1 - 3 * (N - 1))
(N - 2)(N - 3)
}
if Adjusted then
// Mathlab, Minitab and SigmaXL do not add 3 (which is the kurtosis for normal distribution
Result := {3 + }(N - 1) / ((N - 2) * (N - 3)) * ((N + 1) * Result - 3 * (N - 1));
end;
What is the reason for such adjustments and why Delphi decided not to implement it?

Quick Smooth Resizing of Bitmaps

I am trying to write my own quick resampler which allows to scale image down by 2,3,4 etc.
I compared it with StretchBlt and my resampler is about 2 times slower.
My code:
type TRGBA = record
B,G,R: Byte;
A: Byte;
end;
PRGBAArray = ^TRGBAArray;
TRGBAArray = array[0..32767] of TRGBA;
procedure DownsampleSys(Src, Dst: TBitmap; Times: Integer);
var ARect: TRect;
dc:HDC;
p:TPoint;
begin
Dst.Width := Src.Width div Times;
Dst.Height := Src.Height div Times;
ARect := Rect(0,0, Dst.Width, Dst.Height);
dc := Dst.Canvas.Handle;
GetBrushOrgEx(dc,p);
SetStretchBltMode(dc,HALFTONE);
SetBrushOrgEx(dc,p.x,p.y,#p);
StretchBlt(dc,
ARect.Left, ARect.Top,
ARect.Right- ARect.Left, ARect.Bottom- ARect.Top,
Src.Canvas.Handle,0,0,Src.Width,Src.Height,Dst.Canvas.CopyMode);
end;
procedure Downsample2(Src, Dst: TBitmap; Times: Integer);
var x,y: Integer;
xx,yy: Integer;
FromP, ToP: PRGBAArray;
SumR, SumG, SumB: Cardinal;
Times2: Integer;
xTimes, yTimes: Integer;
xxxTimes: Integer;
MarginL, MarginT: Integer;
begin
Dst.Width := floor(Src.Width/ Times);
Dst.Height := floor(Src.Height / Times);
Times2 := Times * Times;
MarginL := (Src.Width - (Dst.Width * Times)) div 2;
MarginT := (Src.Height - (Dst.Height * Times)) div 2;
for y:=0 to Dst.Height-1 do begin
ToP := Dst.Scanline[y];
yTimes := MarginT + y*Times;
for x:=0 to Dst.Width-1 do begin
SumR := 0;
SumG := 0;
SumB := 0;
xTimes := MarginL + x*Times;
for yy:=0 to Times-1 do begin
FromP := Src.Scanline[yy + yTimes];
for xx:=0 to Times-1 do begin
xxxTimes := xx + xTimes;
SumR := SumR + FromP[xxxTimes].R;
SumG := SumG + FromP[xxxTimes].G;
SumB := SumB + FromP[xxxTimes].B;
end;
end;
ToP[x].R := SumR div Times2;
ToP[x].G := SumG div Times2;
ToP[x].B := SumB div Times2;
end;
end;
end;
Usage:
InB := TBitmap.Create;
OutB := TBitmap.Create;
InB.LoadFromFile('2.bmp');
InB.PixelFormat := pf32bit;
OutB.PixelFormat := pf32bit;
Downsample2(InB, OutB, 4);
How can I make it even faster?
If you are still interested in an answer, you could give this thumbnail-routine a try. It's the result of a discussion way back on the Borland newsgroups. On my system it runs a bit faster than Stretch_Halftone, but the box-rescaling is a bit too foggy for my taste. I've abandoned all box-rescaling myself, because the system-rescaling, on my graphics at least, looks better; almost as if it was using bicubic scaling behind the scenes.
The speed gain is by use of lookup-tables, pointer- and integer-math.
// procedure MakeThumbnailMod
// Original source: Roy Magne Klever
// Altered to avoid division by 0
// and tried to make it a bit faster (RS)
//Integer math courtesy of Hagen Redmann
type
PRGB32 = ^TRGB32;
TRGB32 = packed record
b: byte;
g: byte;
r: byte;
a: byte;
end;
TLine32 = array [0 .. maxint div SizeOf(TRGB32) - 1] of TRGB32;
PLine32 = ^TLine32;
TIntArray = array of integer;
TDeltaArray = array of array of integer;
procedure MakeStepsAndWeights(xscale, yscale: Single; xw, yh: integer;
var dxmin, dymin: integer; var Weights: TDeltaArray;
var xsteps, ysteps: TIntArray);
var
i, j: integer;
x1, x2: integer;
dxmax, dymax, intscale: integer;
fact: Single;
begin
SetLength(xsteps, xw);
SetLength(ysteps, yh);
intscale := round(xscale * $10000);
// won't work if xcale > $10000/2, because then intscale
// exceeds 32bit integer. I don't see that happening.
x1 := 0;
x2 := intscale shr 16;
for i := 0 to xw - 1 do
begin
xsteps[i] := x2 - x1;
x1 := x2;
x2 := (i + 2) * intscale shr 16;
end;
dxmin := Ceil(xscale - 1);
dxmax := trunc(xscale + 1);
intscale := round(yscale * $10000);
x1 := 0;
x2 := intscale shr 16;
for i := 0 to yh - 1 do
begin
ysteps[i] := x2 - x1;
x1 := x2;
x2 := (i + 2) * intscale shr 16;
end;
dymin := Ceil(yscale - 1);
dymax := trunc(yscale + 1);
SetLength(weights, dxmax - dxmin + 1, dymax - dymin + 1);
for i := 0 to dxmax - dxmin do
begin
fact := 1 / (dxmin + i);
for j := 0 to dymax - dymin do
weights[i, j] := round(fact / (dymin + j) * $10000);
end;
end;
procedure MakeThumbNailMod(const Src, Dest: TBitmap;
NewWidth, NewHeight: integer);
var
xscale, yscale: Single;
x1: integer;
ix, iy: integer;
totalRed, totalGreen, totalBlue: integer;
ratio: integer;
p: PRGB32;
pt1: PRGB32;
ptrD, ptrS: integer;
x, y: integer;
r1, r2: TRect;
x3: integer;
RowDest, RowSource, RowSourceStart: integer;
weights: TDeltaArray;
xsteps, ysteps: TIntArray;
w, h, dxmin, dymin: integer;
dx, dy: integer;
begin
Dest.PixelFormat := pf32bit;
Src.PixelFormat:=pf32bit; //to be on the safe side
Dest.Width := NewWidth;
Dest.Height := NewHeight;
if (Dest.Width >= Src.Width) or (Dest.Height >= Src.Height) then
begin //we don't do upsampling
r1 := rect(0, 0, Src.Width, Src.Height);
r2 := r1;
OffsetRect(r2, (Dest.Width - Src.Width) div 2,
(Dest.Height - Src.Height) div 2);
Dest.Canvas.CopyRect(r2, Src.Canvas, r1);
exit;
end;
w := Dest.Width;
h := Dest.Height;
ptrD := (w * 32 + 31) and not 31;
ptrD := ptrD div 8; // BytesPerScanline
ptrS := (Src.Width * 32 + 31) and not 31;
ptrS := ptrS div 8;
xscale := Src.Width / w;
yscale := Src.Height / h; // turns div into mults
MakeStepsAndWeights(xscale, yscale, w, h, dxmin, dymin, weights, xsteps, ysteps);
// Make 3 lookup tables for the steps and the ratios
w := w - 1;
h := h - 1;
RowDest := integer(Dest.Scanline[0]);
RowSourceStart := integer(Src.Scanline[0]);
RowSource := RowSourceStart;
for y := 0 to h do
begin
dy := ysteps[y];
x1 := 0;
x3 := 0;
for x := 0 to w do
begin
dx := xsteps[x];
totalRed := 0;
totalGreen := 0;
totalBlue := 0;
RowSource := RowSourceStart;
for iy := 1 to dy do
begin
p := PRGB32(RowSource + x1);
for ix := 1 to dx do
begin
totalRed := totalRed + p^.r;
totalGreen := totalGreen + p^.g;
totalBlue := totalBlue + p^.b; //maybe add the alpha-channel optionally
inc(p);
end;
RowSource := RowSource - ptrS;
end;
pt1 := PRGB32(RowDest + x3);
ratio := weights[dx - dxmin, dy - dymin];
pt1^.r := (totalRed * ratio) shr 16; //"rounding"
pt1^.g := (totalGreen * ratio) shr 16;
pt1^.b := (totalBlue * ratio) shr 16;
x1 := x1 + 4 * dx;
x3 := x3 + 4;
end;
RowDest := RowDest - ptrD;
RowSourceStart := RowSource;
end;
//SharpenMod(Work, Dest, min(1 + 0.4 * (xscale - 1), 2.5));
//The sharpening makes the thumb look nicer, but is omitted here
end;

Delphi - gradial fade of bitmap edges

Any library/code to fade the edges of a bitmap in a gradient manner?
Something like this:
Edit: final code
Ok came up with this code after your example, it's ~10 times faster after optimization with scanlines. Ideally I think I should convert it to use a 32bit bitmap instead and modify the actual alpha layer, but this works for now, ty!
procedure FadeEdges(b: TBitmap; Depth, Start, Col: TColor);
Var f, x, y, i: Integer;
w,h: Integer;
pArrays: Array of pRGBArray;
xAlpha: Array of byte;
sR, sG, sB: Byte;
a,a2: Double;
r1,g1,b1: Double;
Lx,Lx2: Integer;
procedure AlphaBlendPixel(X, Y: Integer);
begin
pArrays[y,x].rgbtRed := Round(r1 + pArrays[y,x].rgbtRed * a2);
pArrays[y,x].rgbtGreen := Round(g1 + pArrays[y,x].rgbtGreen * a2);
pArrays[y,x].rgbtBlue := Round(b1 + pArrays[y,x].rgbtBlue * a2);
end;
procedure AlphaBlendRow(Row: Integer; Alpha: Byte);
Var bR, bG, bB, xA: Byte;
t: Integer;
s,s2: Double;
begin
s := alpha / 255;
s2 := (255 - Alpha) / 255;
for t := 0 to b.Width-1 do begin
bR := pArrays[Row,t].rgbtRed;
bG := pArrays[Row,t].rgbtGreen;
bB := pArrays[Row,t].rgbtBlue;
pArrays[Row,t].rgbtRed := Round(sR*s + bR*s2);
pArrays[Row,t].rgbtGreen := Round(sG*s + bG*s2);
pArrays[Row,t].rgbtBlue := Round(sB*s + bB*s2);
end;
end;
begin
b.PixelFormat := pf24bit;
// cache scanlines
SetLength(pArrays,b.Height);
for y := 0 to b.Height-1 do
pArrays[y] := pRGBArray(b.ScanLine[y]);
// pre-calc Alpha
SetLength(xAlpha,Depth);
for y := 0 to (Depth-1) do
xAlpha[y] := Round(Start + (255 - Start)*y/(Depth-1));
// pre-calc bg color
sR := GetRValue(Col);
sG := GetGValue(Col);
sB := GetBValue(Col);
// offsets
w := b.Width-Depth;
h := b.Height-Depth;
for i := 0 to (Depth-1) do begin
a := xAlpha[i] / 255;
a2 := (255 - xAlpha[i]) / 255;
r1 := sR * a;
g1 := sG * a;
b1 := sB * a;
Lx := (Depth-1)-i;
Lx2 := i+w;
for y := 0 to b.Height - 1 do begin
AlphaBlendPixel(Lx, y); // Left
AlphaBlendPixel(Lx2, y); // right
end;
end;
for i := 0 to (Depth-1) do begin
AlphaBlendRow((Depth-1)-i, xAlpha[i]); // top
AlphaBlendRow(i+(h), xAlpha[i]); // bottom
end;
SetLength(xAlpha,0);
SetLength(pArrays,0);
end;
Final result: (left = original, right = blended on hovering with a ListView)
edit: further speed improvements, twice as fast as original proc.
I can give you some code I wrote a couple of years ago to achieve this. It might be useful as a guide. The code is part of a class that manipulates a bitmap and this is the part that fades the left edge of the bitmap into a white background:
procedure TScreenShotEnhancer.FadeOutLeft(Position, Start: Integer);
var
X, Y: Integer;
F, N: Integer;
I: Integer;
begin
BeginUpdate;
try
N := Position;
for I := 0 to N - 1 do begin
X := Position - I - 1;
F := Round(Start + (255 - Start)*I/N);
for Y := 0 to Height - 1 do
AlphaBlendPixel(X, Y, clWhite, F);
end;
finally
EndUpdate;
end;
end;
The actual work is done in this method:
procedure TScreenShotEnhancer.AlphaBlendPixel(X, Y: Integer; Color: TColor;
Alpha: Byte);
var
backgroundColor: TColor;
displayColor: TColor;
dR, dG, dB: Byte;
bR, bG, bB: Byte;
sR, sG, sB: Byte;
begin
backgroundColor := Bitmap.Canvas.Pixels[X, Y];
bR := GetRValue(backgroundColor);
bG := GetGValue(backgroundColor);
bB := GetBValue(backgroundColor);
sR := GetRValue(Color);
sG := GetGValue(Color);
sB := GetBValue(Color);
dR := Round(sR * alpha / 255 + bR * (255 - alpha) / 255);
dG := Round(sG * alpha / 255 + bG * (255 - alpha) / 255);
dB := Round(sB * alpha / 255 + bB * (255 - alpha) / 255);
displayColor := RGB(dR, dG, dB);
Bitmap.Canvas.Pixels[X, Y] := displayColor;
end;

Add dropshadow to a TBitmap

I have a routine that takes screenshots (TBitmap), I need to add drop-shadow to the final TBitmap/image, I have this code (which used to work but...) something isn't right, the drop-shadow simply isn't drawn:
// --------------------------------------------------------------------- //
procedure TakeScreenshot();
var
lCapRect : TRect;
DestBitmap : TBitmap;
begin
// Take the screenshot & assign it to DestBitmap
// ...
// Add the drop shadow to DestBitmap
DestBitmap.Width := DestBitmap.Width + 6;
DestBitmap.Height := DestBitmap.Height + 6;
PaintShadow(DestBitmap.Canvas, lCapRect);
end;
// --------------------------------------------------------------------- //
procedure PaintShadow(ACanvas : TCanvas; ARect : TRect);
var
AColor : TColor;
i, iMax : Integer;
h1, h2, v1, v2 : Integer;
begin
AColor := ACanvas.Brush.Color;
iMax := 6;
h1 := ARect.Left;
h2 := ARect.Right;
v1 := ARect.Top;
v2 := ARect.Bottom;
with ACanvas do
begin
for i := iMax downto 0 do
begin
ACanvas.Pen.Mode := pmMask;
Pen.Color := DarkenColorBy(AColor, ((iMax - i) * 4 + 10));
MoveTo(h1 + 4{i}, v2 + i);
LineTo(h2 + i + 1, v2 + i);
end; // for
for i := iMax downto 0 do
begin
ACanvas.Pen.Mode := pmMask;
Pen.Color := DarkenColorBy(AColor, ((iMax - i) * 4 + 10));
MoveTo(h2 + i, v1 + 4{i});
LineTo(h2 + i, v2 + i);
end; // for
end; // with
end;
// --------------------------------------------------------------------- //
function Max(const A, B: Integer): Integer;
begin
if (A > B) then
Result := A
else
Result := B;
end;
// --------------------------------------------------------------------- //
function DarkenColorBy(BaseColor : TColor; Amount : Integer) : TColor;
begin
Result := RGB(Max(GetRValue(ColorToRGB(BaseColor)) - Amount, 0),
Max(GetGValue(ColorToRGB(BaseColor)) - Amount, 0),
Max(GetBValue(ColorToRGB(BaseColor)) - Amount, 0));
end;
My question is: How can I fix this (OR anyone know a simple way to add dropshadow to a TBitmap)?
The final image is meant to be saved as bmp/jpg, not shown in a TImage, so I really need to add drop shadow to the image itself.
PS. I'm using Delphi 7 Pro, my app is restricted to Windows XP or later
EDIT
lCapRect depends on the settings (whether I'm capturing the active monitor, window or all the desktop monitors), but let's say it's calculated this way:
lCapRect.Right := Screen.DesktopLeft + Screen.DesktopWidth;
lCapRect.Bottom := Screen.DesktopTop + Screen.DesktopHeight;
lCapRect.Left := Screen.DesktopLeft;
lCapRect.Top := Screen.DesktopTop;
The bitmap does contain the screenshot (+ 6 pixels added to the bottom & right sides to make room for the dropshadow), it's just that the drop shadow drawing doesn't happen
You haven't shown how you are calculating lCapRect. For not drawing off the bitmap regarding your PaintShadow procedure, it has to be smaller than the bitmap, example:
lCapRect := DestBitmap.Canvas.ClipRect;
// Add the drop shadow to DestBitmap
DestBitmap.Width := DestBitmap.Width + 6;
DestBitmap.Height := DestBitmap.Height + 6;
PaintShadow(DestBitmap.Canvas, lCapRect);

converting a PNGImage to grayscale using delphi

hi there
here it is my code:
procedure TForm4.Button1Click(Sender: TObject);
var
png: TPNGImage;
data: PRGBQarray;
p: ^tagRGBQuad;
i, o: integer;
begin
png := TPNGImage.Create;
try
png.LoadFromFile('C:\Untitled.png');
for o := 1 to 100 do
begin
data:=png.Scanline[o];
for I := 1 to 400 do
begin
p := #data^[i];
p.rgbGreen := p.rgbBlue;
p.rgbRed := p.rgbGreen;
end;
end;
img.picture.Assign(png);
finally
png.Free;
end;
end;
it doesn't work and it makes the pic messy, I'm sure it's because of the rgbReserved.
what should i do?
This is how to greyify a bitmap. (And, yes, if you want to greyify a PNG, you first need to get the bitmap data out of it. I think the VCL will do this for you.)
type
PRGB32Array = ^TRGB32Array;
TRGB32Array = packed array[0..MaxInt div SizeOf(TRGBQuad)-1] of TRGBQuad;
procedure MakeGrey(Bitmap: TBitmap);
var
w, h: integer;
y: Integer;
sl: PRGB32Array;
x: Integer;
grey: byte;
begin
Bitmap.PixelFormat := pf32bit;
w := Bitmap.Width;
h := Bitmap.Height;
for y := 0 to h - 1 do
begin
sl := Bitmap.ScanLine[y];
for x := 0 to w - 1 do
with sl[x] do
begin
grey := (rgbBlue + rgbGreen + rgbRed) div 3;
rgbBlue := grey;
rgbGreen := grey;
rgbRed := grey;
end;
end;
end;
Sample usage:
procedure TForm4.Button1Click(Sender: TObject);
var
bm: TBitmap;
begin
bm := TBitmap.Create;
try
bm.LoadFromFile('C:\Users\Andreas Rejbrand\Pictures\Porträtt, litet, kvadratiskt.bmp');
MakeGrey(bm);
Canvas.Draw(0, 0, bm);
finally
bm.Free;
end;
end;
Andreas's answer will give you a good, fast approximation, but you'll lose some quality, because red, green and blue don't mix with equal intensities in the human eye. If you want to "get it right", instead of
grey := (rgbBlue + rgbGreen + rgbRed) div 3;
try this:
grey := round(rgbRed * .3) + round(rgbGreen * .59) + round(rgbBlue * .11);
You'll get a bit of a performance hit over the simple average, though it probably won't be noticeable unless you're on a very large image.
I know the question has already been answered but here is my 2c worth...
The following code comes from the PNGComponents package (PngFunctions.pas) produced by Thany.
//
//The Following code comes from the PNGComponents package from Thany...
//
procedure MakeImageGrayscale(Image: TPNGObject; Amount: Byte = 255);
procedure GrayscaleRGB(var R, G, B: Byte);
var
X: Byte;
begin
X := Round(R * 0.30 + G * 0.59 + B * 0.11);
R := Round(R / 256 * (256 - Amount - 1)) + Round(X / 256 * (Amount + 1));
G := Round(G / 256 * (256 - Amount - 1)) + Round(X / 256 * (Amount + 1));
B := Round(B / 256 * (256 - Amount - 1)) + Round(X / 256 * (Amount + 1));
end;
var
X, Y, PalCount: Integer;
Line: Pointer;
PaletteHandle: HPalette;
Palette: array[Byte] of TPaletteEntry;
begin
//Don't do anything if the image is already a grayscaled one
if not (Image.Header.ColorType in [COLOR_GRAYSCALE, COLOR_GRAYSCALEALPHA])
then begin
if Image.Header.ColorType = COLOR_PALETTE
then begin
//Grayscale every palette entry
PaletteHandle := Image.Palette;
PalCount := GetPaletteEntries(PaletteHandle, 0, 256, Palette);
for X := 0 to PalCount - 1
do GrayscaleRGB(Palette[X].peRed, Palette[X].peGreen, Palette[X].peBlue);
SetPaletteEntries(PaletteHandle, 0, PalCount, Palette);
Image.Palette := PaletteHandle;
end
else begin
//Grayscale every pixel
for Y := 0 to Image.Height - 1
do begin
Line := Image.Scanline[Y];
for X := 0 to Image.Width - 1
do GrayscaleRGB(PRGBLine(Line)^[X].rgbtRed, PRGBLine(Line)^[X].rgbtGreen, PRGBLine(Line)^[X].rgbtBlue);
end;
end;
end;
end;
There is a set of routines, that was originally published by the author of the PNGImage components, that can be found on Code Central that shows how to do other things like Alpha blending two images, rotation, overlay, etc. CodeCentral Link
This really should have been a comment to #Mason's routine to turn RGB into GreyScale, but since I don't know how to make a comment show code, I'm making it an answer instead.
This is how I do the conversion:
FUNCTION RGB2GRAY(R,G,B : BYTE) : BYTE; Register; ASSEMBLER;
ASM
IMUL EAX,19595
IMUL EDX,38470
IMUL ECX,7471
ADD EAX,EDX
ADD EAX,ECX
SHR EAX,16
END;
FUNCTION GreyScale(C : TColor) : TColor; Register; ASSEMBLER;
ASM
MOVZX EDX,AH
MOV ECX,EAX
SHR ECX,16
MOVZX EAX,AL
CALL RGB2GRAY
MOVZX EAX,AL
MOV AH,AL
SHL EAX,8
MOV AL,AH
END;
I don't know if it is NTSC formula or whatever, but they seem to work in my programs :-).

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