How do you scale n images to fit a certain width? - image

Question

I've got 3 images I want to fit on a web page horizontally side by side, they are of various proportions and I want them to end up sharing a particular height (to be calculated). So let's say the width of my page is 't' and the current dimensions of the images are h1 x w1, h2 x w2, h3 x w3
I worked out a formula for 2 images but I can't get my head around 3 or more:
(h1*h2*t) / (w1*h2 + h1*w2)

Answer 1

The condition you must respect is:
k1*w1 + k2*w2 + ... + kn*wn = t
where kn is the scaling constant applied to the width to keep the original proportion of the image with its new height.
We can say that
kn = h_new / hn
where h_new is the new height for all images. From there it's all substitution and isolation
h_new*w1/h1 + h_new*w2/h2 + ... + h_new*wn/hn = t
h_new * (w1/h1 + w2/h2 + ... + wn/hn) = t
h_new = t / (w1/h1 + w2/h2 + ... + wn/hn)
I think that should be it, reply if I'm completely wrong! :)

Answer 2

I wrote a photoshop CS5 script in javascript to resize and save out the open images based on #vache's formula. Hope someone finds it useful:
var outputFolder = Folder.selectDialog("Select a folder for the output files")
if(outputFolder != null) {
var startRulerUnits = app.preferences.rulerUnits
var startDisplayDialogs = app.displayDialogs
// Set Adobe Photoshop CS5 to use pixels and display no dialogs
app.preferences.rulerUnits = Units.PIXELS
app.displayDialogs = DialogModes.NO
do {
var totalWidth = parseInt( prompt("How wide do they need to fit into?", 844) );
}
while(totalWidth <= 0 || isNaN(totalWidth));
var DL = documents.length;
var totalArea = 0;
for(a=0;a<DL;a++){
var cur = documents[a];
totalArea += cur.width / cur.height;
}
var newHeight = totalWidth / totalArea;
for(a=1;a<=DL;a++){
activeDocument = documents[a-1];
var AD=activeDocument;
// bring to front
app.activeDocument = AD;
AD.changeMode(ChangeMode.RGB);
var imgName= AD.name.toLowerCase();
imgName = imgName.substr(0, imgName.length -4);
AD.flatten();
AD.resizeImage(null,UnitValue(newHeight,"px"),null,ResampleMethod.BICUBIC);
//AD.resizeImage(UnitValue(newWidth,"px"),null,null,ResampleMethod.BICUBIC);
saveForWeb(outputFolder, imgName, AD);
}
// Close all the open documents
while (app.documents.length) {
app.activeDocument.close(SaveOptions.DONOTSAVECHANGES)
}
// Reset the application preferences
app.preferences.rulerUnits = startRulerUnits;
app.displayDialogs = startDisplayDialogs;
}
function saveForWeb(outputFolderStr, filename, AD)
{
var opts, file;
opts = new ExportOptionsSaveForWeb();
opts.format = SaveDocumentType.JPEG;
opts.quality = 80;
if (filename.length > 27) {
file = new File(outputFolderStr + "/temp.jpg");
AD.exportDocument(file, ExportType.SAVEFORWEB, opts);
file.rename(filename + ".jpg");
}
else {
file = new File(outputFolderStr + "/" + filename + ".jpg");
AD.exportDocument(file, ExportType.SAVEFORWEB, opts);
}
}