Posted on May 22, 2018

Introduction to Aspose.Imaging, Part 6

In this part I'll tell you about an easier way to rotate an image, how to create multipage TIFFs and how to extract separate frames from an animated GIF file.

Simple rotation.

In addition to transformation matrix-based rotation, there is also a helper method to allow for easy rotation in Aspose.Imaging. The method works on RasterImage and its descendants.

// Load an image to be rotated in an instance of RasterImage using (RasterImage image = (RasterImage)Image.Load("aspose-logo.jpg")) { // Before rotation, the image should be cached for better performance if (!image.IsCached) { image.CacheData(); } // Perform the rotation on 20 degree while keeping the image size proportional with red background color and Save the result to a new file image.Rotate(20f, true, Color.Red); image.Save( "RotatingImageOnSpecificAngle_out.jpg"); }

So you just have to specify rotation angle (clockwise), wether the new image should be resized to fit the rotated content, and what to fill "uncovered" areas with.

Composing multi-frame TIFFs

This is actually also very simple, though the example will be longer. TIFF files allow several properties to be specified, the BitsPerSample property - array specifying number of bits per each channel of a pixel, Orientation property - obvious, Photometric property - specifies a value that defines color interpretation properties of a TIFF - response curves etc., Compression property - obvious - and FillOrder - endianness - property are specified in this example.

List<string> files = new List<string>(new[] { "Frame1.tiff", "Frame2.tiff" }); TiffOptions createOptions = new TiffOptions(TiffExpectedFormat.Default); createOptions.BitsPerSample = new ushort[] { 1 }; createOptions.Orientation = TiffOrientations.TopLeft; createOptions.Photometric = TiffPhotometrics.MinIsBlack; createOptions.Compression = TiffCompressions.CcittFax3; createOptions.FillOrder = TiffFillOrders.Lsb2Msb; TiffImage output = null; List<TiffImage> images = new List<TiffImage>(); try { foreach (var file in files) { // Create an instance of TiffImage and load the source image TiffImage input = (TiffImage)Image.Load(file); images.Add(input); // Do not dispose before data is fetched. Data is fetched on 'Save' later. foreach (var frame in input.Frames) { if (output == null) { // Create a new tiff image with first frame defined. output = new TiffImage(TiffFrame.CopyFrame(frame)); } else { // Add copied frame to destination image output.AddFrame(TiffFrame.CopyFrame(frame)); } } } if (output != null) { // Save the result output.Save("MultiFrameTiff.tif", createOptions); } } finally { foreach (TiffImage image in images) { image.Dispose(); } output.Dispose(); }

Do note that images are only really added to the TIFF image on the Save call, so you should take care not to dispose them before. Here we create copies of the frames anyway.
To remove a frame from TIFF image, call RemoveFrame with index of frame to remove.

Saving a frame from multi-frame GIF

This is also quite simple to do, but the terminology is a bit different - here, frames are put in blocks, which are represented as objects implementing IGifBlock interface. Blocks can be added via AddBlock and removed via RemoveBlock. To add an image as a block you just create a new GifFrameBlock passing image to the constructor. There are also other kinds of blocks. Consequently, here's how you can access them:

Image objImage = Image.Load("sample.gif"); using (GifImage gif = (GifImage)objImage) { // Iterate through arry of blocks in the GIF image for (int i = 0; i < gif.Blocks.Length; i++) { // Convert block to GifFrameBlock class instance GifFrameBlock gifBlock = gif.Blocks[i] as GifFrameBlock; // Check if gif block is then ignore it if (gifBlock == null) { continue; } // Create an instance of TIFF Option class and Save the GIFF block as TIFF image TiffOptions objTiff = new TiffOptions(TiffExpectedFormat.Default); gifBlock.Save("sample_frame_" + i + "_out.tif", objTiff); } }