In the course of doing some image mutilation in Matlab, I had need to perform some blend operations. Prior to that point, I had been using GIMP to perform the task, but I'd rather be able to automate things. There are probably a number of FEX submissions that could replace this function, but like usual, I decided to reinvent the wheel and write my own.
The following function makes available most of the common blend modes available in GIMP or Photoshop, but I decided to add a few extra things. Uncommon features include:
- Adjustable dodge/burn amount (not just opacity!)
- Several luminance-dependent analogs of common functions
- Lightness and Intensity modes
- Several hue permutation modes
- Several color permutation (hue & saturation) modes
- Inputs can be single images or image sequences (4-D inputs!)
This is probably in need of some work still; I'd like to add some sort of alpha support to things perhaps. In the meantime, it's working well. Many of the conversions use colorspace() from Pascal Getreuer.
function outpict=imblend(FG,BG,opacity,blendmode,amount)
% IMBLEND(FG, BG, OPACITY, BLENDMODE,{AMOUNT})
% blend images or imagesets as one would blend layers in GIMP or
% Photoshop.
%
% FG, BG are RGB image arrays of same H,V dimension
% both can be single images or 4-D imagesets of equal length
% can also blend a single image with a 4-D imageset
% mismatches of dimensions 3:4 result in array expansion
% allows blending static overlays with an entire animation
% mismatches of dimensions 1:2 are not supported
% OPACITY is a scalar from 0 to 1
% defines mixing of blended result and original BG
% AMOUNT is a scalar (optional, default 1)
% used to internally scale the influence of blend calculations
% BLENDMODE is a string assignment (see list)
%
%
% MODES:
% normal
% screen
% overlay (standard method)
% softlight (GIMP overlay)
% hardlight
% vividlight
% hardmix (similar to posterization) amount:[0 1]
% posterize (stronger influence from mask)
% colordodge (similar to GIMP dodge) amount:[0 1]
% colorburn (similar to GIMP burn) amount:[0 1]
% lineardodge amount:[0 1]
% linearburn amount:[0 1]
% lighten RGB (lighten only (RGB))
% darken RGB (darken only (RGB))
% lighten Y (lighten only (luma only))
% darken Y (darken only (luma only))
% scale add (add bg to fg deviation from mean) amount:(-inf to +inf)
% scale mult (scale bg by mean-normalized fg) amount:(-inf to +inf)
% multiply
% divide
% addition
% subtraction
% difference
% exclusion
% hue
% saturation
% value
% luma1 (uses colorspace() YIQ conversion)
% luma2 (Image Processing toolbox YIQ conversion)
% lightness (approx identical to intensity)
% intensity
% color
% permute H>H (rotates hue by mask hue) amount:(-inf to +inf)
% permute dH>H (rotates hue by hue difference) amount:(-inf to +inf)
% permute Y>H (rotates hue by mask luma) amount:(-inf to +inf)
% permute dY>H (rotates hue by luma difference) amount:(-inf to +inf)
% permute H>HS (rotates color by mask hue) amount:(-inf to +inf)
% permute dH>HS (rotates color by hue difference) amount:(-inf to +inf)
% permute Y>HS (rotates color by mask luma) amount:(-inf to +inf)
% permute dY>HS (rotates color by luma difference) amount:(-inf to +inf)
%
% NOTE:
% modes which accept 'amount' argument are marked with effective range
% dH>H and dH>HS permutations are same as 'hue' when amount==-1
% color permutations combine hue rotation and saturation blending
% saturation blending is maximized when abs(amount)==1
%
% CLASS SUPPORT:
% Accepts images of 'uint8', 'double', and 'logical'
% Return type is inherited from BG
% In the case of a 'double' input, any image containing values >1
% is assumed to have a white value of 255.
% SOURCES:
% http://www.venture-ware.com/kevin/coding/lets-learn-math-photoshop-blend-modes/
% http://www.deepskycolors.com/archive/2010/04/21/formulas-for-Photoshop-blending-modes.html
% http://en.wikipedia.org/wiki/Blend_modes
% http://en.wikipedia.org/wiki/YUV
% http://www.kineticsystem.org/?q=node/13
% http://www.simplefilter.de/en/basics/mixmods.html
if nargin ~= 5
amount=1;
end
% i had intended to make this more class-insensitive, but i never need it
% output type is inherited from BG, assumes white value of either 1 or 255
inclassFG=class(FG);
inclassBG=class(BG);
if strcmp(inclassFG,'uint8')
fgmax=255;
elseif strcmp(inclassFG,'double')
if max(max(max(FG)))<=1
fgmax=1;
else
fgmax=255;
end
elseif strcmp(inclassFG,'logical')
fgmax=1;
else
disp('IMBLEND: unsupported class for FG')
return
end
if strcmp(inclassBG,'uint8')
bgmax=255;
elseif strcmp(inclassBG,'double')
if max(max(max(BG)))<=1
bgmax=1;
else
bgmax=255;
end
elseif strcmp(inclassBG,'logical')
bgmax=1;
else
disp('IMBLEND: unsupported class for BG')
return
end
% expand along dimension 3 where necessary
if size(FG,3)<size(BG,3)
FG=repmat(FG,[1 1 size(BG,3) 1]);
elseif size(FG,3)>size(BG,3)
BG=repmat(BG,[1 1 size(FG,3) 1]);
end
% check if height & width match
sFG=size(FG);
sBG=size(BG);
if any(sFG(1:2)~=sBG(1:2))
disp('IMBLEND: images of mismatched dimension')
return
end
% check frame count and expand as necessary
if length(sFG)~=4 && length(sBG)~=4 % two single images
images=1;
else
if length(sFG)~=4 % single FG, multiple BG
FG=repmat(FG,[1 1 1 sBG(4)]);
elseif length(sBG)~=4 % multiple FG, single BG
BG=repmat(BG,[1 1 1 sFG(4)]); sBG=size(BG);
elseif sFG(4)~=sBG(4) % two unequal imagesets
disp('IMBLEND: imagesets of unequal length')
return
end
images=sBG(4);
end
% perform blend operations
outpict=zeros(sBG);
for n=1:1:images
I=double(BG(:,:,:,n))/bgmax;
M=double(FG(:,:,:,n))/fgmax;
switch lower(blendmode)
case 'normal'
R=M;
case 'screen'
R=1-((1-M).*(1-I));
case 'overlay' % actual standard overlay mode
hi=I>0.5; lo=I<=0.5;
R=zeros(size(I));
R(lo)=2*I(lo).*M(lo);
R(hi)=1-2*(1-M(hi)).*(1-I(hi));
case 'softlight' % same as GIMP 'overlay' due to legacy bug
Rs=1-((1-M).*(1-I));
R=(I.*((1-I).*M+Rs));
case 'hardlight'
hi=M>0.5; lo=M<=0.5;
R=zeros(size(I));
R(lo)=2*I(lo).*M(lo);
R(hi)=1-2*(1-M(hi)).*(1-I(hi));
case 'vividlight' % test this; example formulae are inconsistent
hi=M>0.5; lo=M<=0.5;
R=zeros(size(I));
R(lo)=1-(1-I(lo))./(2*M(lo));
R(hi)=I(hi)./(1-2*(M(hi)-0.5));
case 'posterize' % actually a broken version of vividlight
hi=M>0.5; lo=M<=0.5;
R=zeros(size(I));
R(lo)=(1-I(lo))./(2*(M(lo)-0.5));
R(hi)=1-I(hi)./(1-2*M(hi));
case 'hardmix' % ps mode similar to posterization
amount=max(min(amount,1),0);
Rs=M+I;
R=Rs;
R(Rs>1)=1*amount;
R(Rs<1)=0;
% DODGES/BURNS
case'colordodge'
amount=max(min(amount,1),0);
R=I./(1-M*amount);
case 'colorburn'
amount=max(min(amount,1),0);
R=1-(1-I)./(M*amount+(1-amount));
case 'lineardodge' % addition
amount=max(min(amount,1),0);
R=M*amount+I;
case 'linearburn'
amount=max(min(amount,1),0);
R=M*amount+I-1*amount;
% SIMPLE MATH OPS
case 'lighten rgb' % lighten only (RGB, no luminance)
R=max(I,M);
case 'darken rgb' % darken only (RGB, no luminance)
R=min(I,M);
case 'lighten y' % lighten only (based on luminance)
Myiq=colorspace('RGB->YIQ',M);
Iyiq=colorspace('RGB->YIQ',I);
mask=Myiq(:,:,1)>Iyiq(:,:,1);
R=double(replacepixels(255*I,mask,255*M))/255;
case 'darken y' % darken only (based on luminance)
Myiq=colorspace('RGB->YIQ',M);
Iyiq=colorspace('RGB->YIQ',I);
mask=Myiq(:,:,1)<Iyiq(:,:,1);
R=double(replacepixels(255*I,mask,255*M))/255;
case 'multiply'
R=M.*I;
case 'divide'
R=I./(M+1E-3);
case 'addition' % same as lineardodge
R=M+I;
case 'subtraction'
R=I-M;
case 'difference'
R=abs(M-I);
case 'exclusion'
R=M+I-2*M.*I;
case 'hue'
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=Mhsv(:,:,1);
R=hsv2rgb(Rhsv);
case 'saturation'
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,2)=Mhsv(:,:,2);
R=hsv2rgb(Rhsv);
% V=max([R G B])
% L=mean(max([R G B]),min([R G B]))
% I=mean([R G B])
% Y=[0.299 0.587 0.114]*[R G B]'
case 'value'
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,3)=Mhsv(:,:,3);
R=hsv2rgb(Rhsv);
% all colorspace() Y-swaps produce identical results within 1 LSB
% (YUV, YIQ, YCbCr, YPbPr, YDbDr)
case 'luma1' % swaps fg bg luma
Myiq=colorspace('RGB->YIQ',M);
Ryiq=colorspace('RGB->YIQ',I);
Ryiq(:,:,1)=Myiq(:,:,1);
R=colorspace('RGB<-YIQ',Ryiq);
case 'luma2' % swaps fg bg luma (using IP toolbox)
Myiq=rgb2ntsc(M);
Ryiq=rgb2ntsc(I);
Ryiq(:,:,1)=Myiq(:,:,1);
R=ntsc2rgb(Ryiq);
% L and I swaps are calculated differently,
% but results are practically identical (within 1 LSB)
% for all available HSL and HSI conversion implementations
case 'lightness' % swaps fg bg lightness
Mhsl=colorspace('RGB->HSL',M);
Rhsl=colorspace('RGB->HSL',I);
Rhsl(:,:,3)=Mhsl(:,:,3);
R=colorspace('RGB<-HSL',Rhsl);
case 'intensity' % swaps fg bg intensity
Mhsi=colorspace('RGB->HSI',M);
Rhsi=colorspace('RGB->HSI',I);
Rhsi(:,:,3)=Mhsi(:,:,3);
R=colorspace('RGB<-HSI',Rhsi);
case 'color' % same as GIMP, swap H&S
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1:2)=Mhsv(:,:,1:2);
R=hsv2rgb(Rhsv);
% HUE PERMUTATIONS
case 'permute y>h' % permutes bg hue based on fg luma
factors=[0.299 0.587 0.114];
osize=size(M(:,:,1));
cscale=repmat(reshape(factors,1,1,3),[osize 1]);
Y=sum(M.*cscale,3);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+Y*amount,1);
R=hsv2rgb(Rhsv);
case 'permute h>h' % permutes bg hue based on fg hue
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+Mhsv(:,:,1)*amount,1);
R=hsv2rgb(Rhsv);
case 'permute dy>h' % permutes bg hue based on luma difference
factors=[0.299 0.587 0.114];
osize=size(M(:,:,1));
cscale=repmat(reshape(factors,1,1,3),[osize 1]);
Ym=sum(M.*cscale,3);
Yi=sum(I.*cscale,3);
dY=Yi-Ym;
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+dY*amount,1);
R=hsv2rgb(Rhsv);
% note that dH+H permutation is same as a hue swap when amount==-1
case 'permute dh>h' % permutes bg hue based on hue difference
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
dH=Rhsv(:,:,1)-Mhsv(:,:,1);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+dH*amount,1);
R=hsv2rgb(Rhsv);
% COLOR PERMUTATIONS (rotate hue and blend saturation)
case 'permute y>hs' % permutes bg color based on fg luma
factors=[0.299 0.587 0.114];
osize=size(M(:,:,1));
cscale=repmat(reshape(factors,1,1,3),[osize 1]);
Y=sum(M.*cscale,3);
amt=max(min(abs(amount),1),0); % needed since S-blending has limited range
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+Y*amount,1);
Rhsv(:,:,2)=amt*Mhsv(:,:,2)+(1-amt)*Rhsv(:,:,2);
R=hsv2rgb(Rhsv);
case 'permute h>hs' % permutes bg color based on fg hue
amt=max(min(abs(amount),1),0); % needed since S-blending has limited range
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+Mhsv(:,:,1)*amount,1);
Rhsv(:,:,2)=amt*Mhsv(:,:,2)+(1-amt)*Rhsv(:,:,2);
R=hsv2rgb(Rhsv);
case 'permute dy>hs' % permutes bg color based on luma difference
factors=[0.299 0.587 0.114];
osize=size(M(:,:,1));
cscale=repmat(reshape(factors,1,1,3),[osize 1]);
Ym=sum(M.*cscale,3);
Yi=sum(I.*cscale,3);
dY=Yi-Ym;
amt=max(min(abs(amount),1),0); % needed since S-blending has limited range
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+dY*amount,1);
Rhsv(:,:,2)=amt*Mhsv(:,:,2)+(1-amt)*Rhsv(:,:,2);
R=hsv2rgb(Rhsv);
% note that dH+H permutation is same as a hue swap when amount==-1
case 'permute dh>hs' % permutes bg color based on hue difference
amt=max(min(abs(amount),1),0); % needed since S-blending has limited range
Mhsv=rgb2hsv(M);
Rhsv=rgb2hsv(I);
dH=Rhsv(:,:,1)-Mhsv(:,:,1);
Rhsv(:,:,1)=mod(Rhsv(:,:,1)+dH*amount,1);
Rhsv(:,:,2)=amt*Mhsv(:,:,2)+(1-amt)*Rhsv(:,:,2);
R=hsv2rgb(Rhsv);
% SCALE ADD treats FG as an additive gain map with a null point at its mean
case 'scale add'
Mstretch=imadjust(M,stretchlim(M));
centercolor=mean(mean(Mstretch,1),2);
R=zeros(size(I));
for c=1:1:3;
R(:,:,c)=I(:,:,c)+(Mstretch(:,:,c)-centercolor(:,:,c))*amount;
end
% SCALE MULT treats FG as a gain map with a null point at its mean
case 'scale mult'
Mstretch=imadjust(M,stretchlim(M));
centercolor=mean(mean(Mstretch,1),2);
R=zeros(size(I));
for c=1:1:3;
R(:,:,c)=I(:,:,c).*(Mstretch(:,:,c)./centercolor(:,:,c))*amount;
end
otherwise
disp('IMBLEND: unknown blend mode');
return
end
R=min(R,1);
R=max(R,0);
R(isnan(R))=1;
outpict(:,:,:,n)=bgmax*(opacity*R + I*(1-opacity));
end
outpict=cast(outpict,inclassBG);
return
I've been thinking about putting some polish on the rest of my image-garbling toolbox, so maybe I'll reveal some examples in time. I've also been toying with the idea of doing some animated plots of large datasets. That may be interesting.
No comments:
Post a Comment