Setting the last element in the array to 0.0 does not guarantee that the image will be saved without a loss of quality. See Saving JPEG 2000 and JPX Images in Lossless Mode for more details.

If some entries of the QUALITY_LAYERS array are very close to each other, and the image is not big, the corresponding quality layers may end up containing no image data.

ImageGear skips creation of empty quality layers. This has no impact on the saved image quality, but slightly reduces the coding time and the saved file size. Example:

Dim format As
IGFormatParams
Dim parameter As
IGControlParameter
Set format =
frmMain.IGFormatsCtl1.S
ettings.GetFormatRef(IG
_FORMAT_JPEG2K)
Set parameter =
format.GetParamCopy("QU
ALITY_LAYERS")
parameter.value.Array.C
hangeAttrs
IG_DATA_DOUBLE, 3
parameter.value.Array.D
ouble(0) = 0.01
parameter.value.Array.D
ouble(1) = 0.1
parameter.value.Array.D
ouble(2) = 0.5
format.UpdateParamFrom
parameter

If the source image dimensions are 800 x 600 = 480000 pixels, the array used in the example will result in the following layer sizes:

• 1st layer: 480000 * 0.01 / 8 = 600 bytes
• 1st and 2nd layers: 480000 * 0.1 / 8 = 6000 bytes
• 1st, 2nd, and 3rd layers (whole codestream): 480000 * 0.5 / 8 = 30000 bytes

Using the same non-zero value for different images causes the filter to write files with a different compression rate. In order to provide a consistent compression rate across images of different sizes, calculate this parameter for each image, based on the product of the image width and height, or on the uncompressed DIB size.

Alternatively, use QUALITY_LAYERS control parameter, which uses relative coefficients.

Setting RATE_BYTES to 0 does not guarantee that the image will be saved without a loss of quality. See Saving JPEG 2000 and JPX Images in Lossless Mode for more details.

The library allows you to save no resolution information, Display Resolution only, or both Display and Capture resolution. It does not allow saving Capture Resolution without saving Display Resolution. If Capture Resolution is known at the time of saving, but Display resolution is not known, the library writes equal values for Display and Capture resolutions.

IIGFormats Interface.LoadPageFromFile Method always loads the whole image.

It is recommended that you do not disable writing the version information, as it could provide helpful hints for future decoders.

Selecting the IG_JPEG2K_FILTER_REVERSIBLE filter does not guarantee that the image will be saved without a loss of quality. See Saving JPEG 2000 and JPX Images in Lossless Mode for more details.

Applying irreversible transform to indexed (paletted) images may result in significant degradation of image quality, because small changes in pixel values may result in significant visual difference after application of a palette. Consider using reversible transform for paletted images, or promoting images to True color and then using the reversible transform.