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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 | 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: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 255inclassFG=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; endelseif strcmp(inclassFG,'logical') fgmax=1;else disp('IMBLEND: unsupported class for FG') returnendif strcmp(inclassBG,'uint8') bgmax=255;elseif strcmp(inclassBG,'double') if max(max(max(BG)))<=1 bgmax=1; else bgmax=255; endelseif strcmp(inclassBG,'logical') bgmax=1;else disp('IMBLEND: unsupported class for BG') returnend% expand along dimension 3 where necessaryif 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 matchsFG=size(FG);sBG=size(BG); if any(sFG(1:2)~=sBG(1:2)) disp('IMBLEND: images of mismatched dimension') returnend% check frame count and expand as necessaryif 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 operationsoutpict=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));endoutpict=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.
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