How to create a Gradientcolor from two existing swatches

Question

Hello all,
I have 2 colors in the swatches palette.has anyone how to create a new gradient color from this to swatches.
So far I can get my to colors from the palette and extract their color:
aSwatch1 = sAISwatchList->GetSwatchByName( colList, colorName1 );
aSwatch2 = sAISwatchList->GetSwatchByName( colList, colorName1 );
iErr = sAISwatchList->GetAIColor( aSwatch1, &colorP1);
iErr = sAISwatchList->GetAIColor( aSwatch2, &colorP2);
// now somehow create a new gradient:
iErr = sAIGradient->NewGradient( &gradientHnd );
but what do now. to get the new color from colorP1 and colorP2. I need a simple linear gradient.
Any hints?
regards
Michael

Answer 1

Hello,
> Please, excuse any ignorance below. I'm not well versed in the actual artistic side of Illustrator, just the implementation
excused because you're the one of the few people here who give thoe most usefull answers
> Isn't that to be expected though? From my admittedly limited understanding, the gradient being saved is really just a sequence of colour stops. I would have thought since the angle of the gradient is more of a property of how its applied to the path (or whatever) that it wouldn't make sense to save it on the gradient colour.
No, not from my view (and needs ).
The color for the gradient has a type of AIGradientStyleMap. this struct contains the angle für the linear gradient etc. This color is added to the swatchpalette so it shoud keep the value.
If you replace the CreateGradientSwatch function in SnpGradien.cpp of the SnippetRunner with the following code a 2nd swatch with an different angle is added to the swatchpalette when creating a new linear gradient is created (name seems not what it should but 2 swatches are created. Applying this 2 swatches to a rectangle also the angle is changed as it should be.
So from my point of view Illustrator doesn't take the angle when a new color/swatch is created in the swatch panel. Why the angle is saved by creating a style is another question and difficult to answer without looking inside the source of Illustrator
ASErr SnpGradient::CreateGradientSwatch(const AIGradientHandle gradient, AISwatchRef& swatch)
ASErr result = kNoErr;
try {
// Insert new swatch at end of general swatch group.
swatch = sAISwatchList->InsertNthSwatch(NULL, -1);
// Get gradient name.
ai::UnicodeString gradientName;
result = sAIGradient->GetGradientName(gradient, gradientName);
aisdk::check_ai_error(result);
// Set swatch name.
result = sAISwatchList->SetSwatchName(swatch, gradientName);
aisdk::check_ai_error(result);
// Create the swatch color using the gradient.
AIColor swatchColor;
swatchColor.kind = kGradient;
swatchColor.c.b.gradient = gradient;
swatchColor.c.b.gradientAngle = 30;
swatchColor.c.b.gradientLength = 1;
AIRealPoint origin = {0,0};
swatchColor.c.b.gradientOrigin = origin;
swatchColor.c.b.hiliteAngle = 0;
swatchColor.c.b.hiliteLength = 0;
SnippetRunnerLog::Instance()->WritePrintf("gradientAngle: %.1f",swatchColor.c.b.gradientAngle);
SnippetRunnerLog::Instance()->WritePrintf("gradientLength: %.1f",swatchColor.c.b.gradientLength);
SnippetRunnerLog::Instance()->WritePrintf("gradientOrigin (v / h): %.1f /  %.1f", swatchColor.c.b.gradientOrigin.v, swatchColor.c.b.gradientOrigin.h);
SnippetRunnerLog::Instance()->WritePrintf("gradientAngle: %.1f",swatchColor.c.b.gradientAngle);
SnippetRunnerLog::Instance()->WritePrintf("hiliteLength: %.1f",swatchColor.c.b.hiliteLength);
// Set the swatch color.
result = sAISwatchList->SetAIColor(swatch, &swatchColor);
aisdk::check_ai_error(result);
// making a 2nd swatch
AISwatchRef swatch2;
swatch2 = sAISwatchList->InsertNthSwatch(NULL, -1);
result = sAISwatchList->SetSwatchName(swatch2, (ai::UnicodeString("Grad2")));
  // Create the swatch color using the gradient.
  AIColor swatchColor2;
  swatchColor2.kind = kGradient;
  swatchColor2.c.b.gradient = gradient;
  swatchColor2.c.b.gradientAngle = 60;
  swatchColor2.c.b.gradientLength = 1;
  swatchColor2.c.b.gradientOrigin = origin;
  swatchColor2.c.b.hiliteAngle = 0;
  swatchColor2.c.b.hiliteLength = 0;
result = sAISwatchList->SetAIColor(swatch2, &swatchColor2);
catch (ai::Error& ex) {
result = ex;
return result;
The CS3/CS4 question is easy: for CS3 i use the CS3 SDK and for CS4 I#m working with the CS4 SDK :-)