// Shamelessly copied from React-Native: https://github.com/facebook/react-native/blob/2cbc9127560c5f0f89ae5aa6ff863b1818f1c7c3/Libraries/Image/RCTImageUtils.m
public static UIImage ToImage(this NSData data, CGSize destSize, nfloat destScale, RCTResizeMode resizeMode = RCTResizeMode.ScaleAspectFit, ImageInformation imageinformation = null, bool allowUpscale = false)
{
using (var sourceRef = CGImageSource.FromData(data))
{
var imageProperties = GetImageProperties(sourceRef);
if (imageProperties == null)
{
throw new BadImageFormatException("Image is null");
}
if (imageinformation != null)
{
if (imageProperties.PixelWidth.HasValue && imageProperties.PixelHeight.HasValue)
{
imageinformation.SetOriginalSize(imageProperties.PixelWidth.Value, imageProperties.PixelHeight.Value);
}
}
var sourceSize = new CGSize((nfloat)imageProperties.PixelWidth, (nfloat)imageProperties.PixelHeight);
if (destSize.IsEmpty)
{
destSize = sourceSize;
if (destScale <= 0)
{
destScale = 1;
}
}
else if (destScale <= 0)
{
destScale = ScaleHelper.Scale;
}
// Calculate target size
CGSize targetSize = RCTTargetSize(sourceSize, 1, destSize, destScale, resizeMode, allowUpscale);
CGSize targetPixelSize = RCTSizeInPixels(targetSize, destScale);
int maxPixelSize = (int)Math.Max(
Math.Min(sourceSize.Width, targetPixelSize.Width),
Math.Min(sourceSize.Height, targetPixelSize.Height)
);
var options = new CGImageThumbnailOptions()
{
ShouldAllowFloat = true,
CreateThumbnailWithTransform = true,
CreateThumbnailFromImageAlways = true,
MaxPixelSize = maxPixelSize,
ShouldCache = false,
};
UIImage image = null;
// gif
if (sourceRef.ImageCount > 1)
{
image = GifHelper.AnimateGif(sourceRef, destScale);
}
else
{
// Get thumbnail
using (var imageRef = sourceRef.CreateThumbnail(0, options))
{
if (imageRef != null)
{
// Return image
image = new UIImage(imageRef, destScale, UIImageOrientation.Up);
}
}
}
if (imageinformation != null && image != null)
{
int width = (int)image.Size.Width;
int height = (int)image.Size.Height;
imageinformation.SetCurrentSize(width.PointsToPixels(), height.PointsToPixels());
}
return(image);
}
}
protected async override Task <UIImage> GenerateImageAsync(string path, ImageSource source, Stream imageData, ImageInformation imageInformation, bool enableTransformations, bool isPlaceholder)
{
UIImage imageIn = null;
if (imageData == null)
{
throw new ArgumentNullException(nameof(imageData));
}
ThrowIfCancellationRequested();
try
{
// Special case to handle WebP decoding on iOS
string ext = null;
if (!string.IsNullOrWhiteSpace(path))
{
if (source == ImageSource.Url)
{
ext = Path.GetExtension(new Uri(path).LocalPath).ToLowerInvariant();
}
else
{
ext = Path.GetExtension(path).ToLowerInvariant();
}
}
if (source != ImageSource.Stream && ext == ".webp")
{
imageIn = new WebP.Touch.WebPCodec().Decode(imageData);
}
// Special case to handle gif animations on iOS
else if (source != ImageSource.Stream && ext == ".gif")
{
using (var nsdata = NSData.FromStream(imageData))
imageIn = GifHelper.AnimateGif(nsdata);
}
else
{
var nsdata = NSData.FromStream(imageData);
int downsampleWidth = Parameters.DownSampleSize?.Item1 ?? 0;
int downsampleHeight = Parameters.DownSampleSize?.Item2 ?? 0;
if (Parameters.DownSampleUseDipUnits)
{
downsampleWidth = downsampleWidth.PointsToPixels();
downsampleHeight = downsampleHeight.PointsToPixels();
}
imageIn = nsdata.ToImage(new CoreGraphics.CGSize(downsampleWidth, downsampleHeight), ScaleHelper.Scale, NSDataExtensions.RCTResizeMode.ScaleAspectFill, imageInformation);
}
}
finally
{
imageData?.Dispose();
}
ThrowIfCancellationRequested();
if (enableTransformations && Parameters.Transformations != null && Parameters.Transformations.Count > 0)
{
var transformations = Parameters.Transformations.ToList();
await _decodingLock.WaitAsync().ConfigureAwait(false); // Applying transformations is both CPU and memory intensive
try
{
foreach (var transformation in transformations)
{
ThrowIfCancellationRequested();
var old = imageIn;
try
{
var bitmapHolder = transformation.Transform(new BitmapHolder(imageIn), path, source, isPlaceholder, Key);
imageIn = bitmapHolder.ToNative();
}
catch (Exception ex)
{
Logger.Error(string.Format("Transformation failed: {0}", transformation.Key), ex);
throw;
}
finally
{
if (old != null && old != imageIn && old.Handle != imageIn.Handle)
{
old.Dispose();
}
}
}
}
finally
{
_decodingLock.Release();
}
}
return(imageIn);
}
