| GetBitmap Function | ||
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Render one or more layers on the current page
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Syntax
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[C#]
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may
throw Exception()Params
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Notes
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Render one or more layers on the current page. This function renders a set of layers and returns the result as a System.Drawing.Bitmap. The Bitmap covers the smallest possible area which encompasses all the layers provided. If this Page is not in a Doc then an exception will be raised. The function will return null if the layers argument is null or empty or the output Bitmap would be smaller than one pixel in area. Rendering options such as resolution are taken directly from the current Doc.Rendering settings. However automatic page rotation (XRendering.AutoRotate) is disabled so that a Layer can be rendered and then re-inserted into the page as a raster copy of itself. Note that a layer can exist on multiple pages and indeed can be rendered in the context of a page that does not currently contain it. However layers typically contain references to named resources which are only available in the context of a specific page. So rendering a layer in the context of a page which does not normally contain it is prone to error unless the page and layer have been specifically constructed to allow this.
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Example
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The following example shows how to use this method to generate various types of drop shadows.
using var doc = new Doc();
// light blue background
doc.Color.SetCmyk(50, 0, 0, 0);
doc.FillRect();
doc.Color.SetRgb(0, 0, 0);
doc.Rect.Inset(20, 20);
doc.Rect.Pin = XRect.Corner.TopLeft;
doc.Rect.Height = doc.Rect.Height / 5;
// set up styles
doc.TextStyle.Size = 72;
double shift = doc.TextStyle.Size * 0.1;
var pink = new XColor();
pink.SetRgb(255, 128, 128);
var gray = new XColor();
gray.SetRgb(128, 128, 128);
var blue = new XColor();
blue.SetRgb(0, 0, 255);
// add text content
AddDropShadow(doc, doc.AddText("Sharp Shadow"), 0, shift, -shift, gray);
doc.Rect.Move(0, -doc.Rect.Height);
AddDropShadow(doc, doc.AddText("Blurred Shadow"), 1, shift, -shift, gray);
doc.Rect.Move(0, -doc.Rect.Height);
AddDropShadow(doc, doc.AddText("Pink Shadow"), 1, shift, -shift, pink);
doc.Rect.Move(0, -doc.Rect.Height);
// add drawn content
doc.Transform.Magnify(0.5, 0.5, 0, 0);
doc.Transform.Translate(50, 0);
string star = "124 158 300 700 476 158 15 493 585 493 124 158";
doc.Width = 20;
doc.Color.String = "255 0 0";
AddDropShadow(doc, doc.AddPoly(star, false), 3, shift, -shift, blue);
doc.Save(Server.MapPath("dropshadows.pdf"));
The code above utilises the following AddDropShadow method.
void AddDropShadow(Doc doc, int id, double gaussianBlurRadius, double shadowHorizontalShift, double shadowVerticalShift, XColor shadowColor) {
string rect = doc.Rect.String;
string transform = doc.Transform.String;
string color = doc.Color.String;
double dpiX = doc.Rendering.DotsPerInchX;
double dpiY = doc.Rendering.DotsPerInchY;
bool saveAlpha = doc.Rendering.SaveAlpha;
int docLayer = doc.Layer;
try {
doc.Rendering.DotsPerInch = 72;
doc.Rendering.SaveAlpha = true;
var layer = doc.ObjectSoup[id] as Layer;
var page = doc.ObjectSoup[doc.Page] as Page;
var bm = page.GetBitmap(new Layer[] { layer });
// expand image if blur may move content off edges
int border = 0;
if (gaussianBlurRadius > 0) {
// we extend our border out two standard deviations
border = (int)Math.Round(Math.Abs(gaussianBlurRadius)) * 2;
int borders = border * 2;
var larger = new Bitmap(bm.Width + borders, bm.Height + borders, bm.PixelFormat);
larger.SetResolution(bm.HorizontalResolution, bm.VerticalResolution);
using (var graphics = Graphics.FromImage(larger)) {
graphics.DrawImage(bm, new Point(border, border));
if (bm != null)
bm.Dispose();
bm = larger;
}
}
doc.Transform.Reset();
doc.Rect.String = layer.Rect.String;
doc.Rect.Inset(-border, -border);
doc.Rect.Move(shadowHorizontalShift, shadowVerticalShift);
doc.Layer = docLayer + 1;
int pid = doc.AddImageBitmap(bm, true);
bm.Dispose();
// Here we set the base image to be one pixel of an appropriate color.
// This is what will determine the shadow color.
var img = doc.ObjectSoup[pid] as ImageLayer;
var pm = img.PixMap;
pm.ClearData(); // this will remove any compression settings
pm.SetData(new byte[] { (byte)shadowColor.Red, (byte)shadowColor.Green, (byte)shadowColor.Blue });
pm.Width = 1;
pm.Height = 1;
// The alpha channel is held as a separate soft mask and this is what will
// determine the shape of the shadow. If required we blur it to give it
// soft edges.
var alpha = pm.SMask;
if (gaussianBlurRadius > 0) {
using (EffectOperation effect = new EffectOperation("Gaussian Blur")) {
effect.Parameters["Radius"].Value = gaussianBlurRadius;
effect.Apply(alpha);
}
}
}
finally {
doc.Rect.String = rect;
doc.Transform.String = transform;
doc.Color.String = color;
doc.Rendering.DotsPerInchX = dpiX;
doc.Rendering.DotsPerInchY = dpiY;
doc.Rendering.SaveAlpha = saveAlpha;
doc.Layer = docLayer;
}
}
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