What are the meanings of itextpdf pdfcontentbyte addtemplate's parameters - itext

Question

I am using itextpdf to merge some pdfs to a single one.
What are the meanings of itextpdf pdfcontentbyte addtemplate's parameters,there is no docs to describe them.

Answer 1

public void addTemplate(PdfTemplate template,
double a, double b, double c, double d, double e, double f)
The six values a, b, c, d, e, and f are elements of a matrix that has three rows and three columns.
You can use this matrix to express a transformation in a two-dimentional system.
Carrying out this multiplication results in this:
x' = a * x + c * y + e
y' = b * x + d * y + f
The third column in the matrix is fixed: you're working in two dimensions, so you don't need to calculate a new z coordinate.
When studying analytical geometry in high school, you've probably learned how to apply transformations to objects.
In PDF, we use a slightly different approach: instead of transforming objects, we transform the coordinate system.
The e and the f value can be used for a translation. The a, b, c, and d value can be used for a rotation and/or scaling operation.
By default the Current Transformation Matrix (CTM) is:
With the addTemplate() method, you can add a Form XObject to a canvas and define a position using e, f, e.g:
canvas.addTemplate(template, 36, 36);
This will add template at coordinate x = 36; y = 36.
By introducing a, b, c, and d, you can also rotate and/or scale the template.
Update: as mentioned in the comments, you might want to use the overloaded methods that accept an AffineTransform parameter if you don't like the Algebra of the transformation matrix.

Answer 2

the code below did the trick,thank for the guys who helped me.
FileInputStream pdfInput = new FileInputStream(pdf);
PdfReader pdfReader = new PdfReader(pdfInput);
for (int index = 1; index <= pdfReader.getNumberOfPages(); index++) {
main.newPage();
PdfImportedPage page = pdfWriter.getImportedPage(pdfReader,
index);
Rectangle pagesize = pdfReader.getPageSizeWithRotation(index);
float oWidth = pagesize.getWidth();
float oHeight = pagesize.getHeight();
float scale = getScale(oWidth, oHeight);
float scaledWidth = oWidth * scale;
float scaledHeight = oHeight * scale;
int rotation = pagesize.getRotation();
AffineTransform transform = new AffineTransform(scale, 0, 0, scale, 0, 0);
switch (rotation) {
case 0:
cb.addTemplate(page, transform);
break;
case 90:
AffineTransform rotate90 = new AffineTransform(0, -1f, 1f, 0, 0, scaledHeight);
rotate90.concatenate(transform);
cb.addTemplate(page, rotate90);
break;
case 180:
AffineTransform rotate180 = new AffineTransform(-1f, 0, 0, -1f, scaledWidth,
scaledHeight);
rotate180.concatenate(transform);
cb.addTemplate(page, rotate180);
break;
case 270:
AffineTransform rotate270 = new AffineTransform(0, 1f, -1f, 0, scaledWidth, 0);
rotate270.concatenate(transform);
cb.addTemplate(page, rotate270);
break;
default:
cb.addTemplate(page, scale, 0, 0, scale, 0, 0);
}
}
private static float getScale(float width, float height) {
float scaleX = PageSize.A4.getWidth() / width;
float scaleY = PageSize.A4.getHeight() / height;
return Math.min(scaleX, scaleY);
}