public void TestIsMetaDataAvailable()
{
EncodedImage encodedImage1 = new EncodedImage(_byteBufferRef);
EncodedImage encodedImage2 = new EncodedImage(_byteBufferRef);
encodedImage2.RotationAngle = 1;
encodedImage2.Width = 1;
encodedImage2.Height = 1;
Assert.IsFalse(EncodedImage.IsMetaDataAvailable(encodedImage1));
Assert.IsTrue(EncodedImage.IsMetaDataAvailable(encodedImage2));
}
internal static float DetermineDownsampleRatio(
ImageRequest imageRequest, EncodedImage encodedImage)
{
Preconditions.CheckArgument(EncodedImage.IsMetaDataAvailable(encodedImage));
ResizeOptions resizeOptions = imageRequest.ResizeOptions;
if (resizeOptions == null || resizeOptions.Height <= 0 || resizeOptions.Width <= 0 ||
encodedImage.Width == 0 || encodedImage.Height == 0)
{
return(1.0f);
}
int rotationAngle = GetRotationAngle(imageRequest, encodedImage);
bool swapDimensions = rotationAngle == 90 || rotationAngle == 270;
int widthAfterRotation = swapDimensions ?
encodedImage.Height : encodedImage.Width;
int heightAfterRotation = swapDimensions ?
encodedImage.Width : encodedImage.Height;
float widthRatio = ((float)resizeOptions.Width) / widthAfterRotation;
float heightRatio = ((float)resizeOptions.Height) / heightAfterRotation;
float ratio = Math.Max(widthRatio, heightRatio);
Debug.Write(string.Format(
"Downsample - Specified size: {0}x{1}, image size: {2}x{3} ratio: {4} x {5}, ratio: {6} for {7}",
resizeOptions.Width,
resizeOptions.Height,
widthAfterRotation,
heightAfterRotation,
widthRatio,
heightRatio,
ratio,
imageRequest.SourceUri.ToString()));
return(ratio);
}
/// <summary>
/// Get the factor between the dimensions of the encodedImage
/// (actual image) and the ones of the imageRequest
/// (requested size).
/// </summary>
/// <param name="imageRequest">
/// The request containing the requested dimensions.
/// </param>
/// <param name="encodedImage">
/// The encoded image with the actual dimensions.
/// </param>
public static int DetermineSampleSize(ImageRequest imageRequest, EncodedImage encodedImage)
{
if (!EncodedImage.IsMetaDataAvailable(encodedImage))
{
return(DEFAULT_SAMPLE_SIZE);
}
float ratio = DetermineDownsampleRatio(imageRequest, encodedImage);
int sampleSize;
if (encodedImage.Format == ImageFormat.JPEG)
{
sampleSize = RatioToSampleSizeJPEG(ratio);
}
else
{
sampleSize = RatioToSampleSize(ratio);
}
// Check the case when the dimension of the downsampled image
// is still larger than the max possible dimension for an image.
int maxDimension = Math.Max(encodedImage.Height, encodedImage.Width);
while (maxDimension / sampleSize > MAX_BITMAP_SIZE)
{
if (encodedImage.Format == ImageFormat.JPEG)
{
sampleSize *= 2;
}
else
{
sampleSize++;
}
}
return(sampleSize);
}
