$gridSampler
$gridSampler
Implementations of this class can, given locations of finder patterns for a QR code in an image, sample the right points in the image to reconstruct the QR code, accounting for perspective distortion. It is abstracted since it is relatively expensive and should be allowed to take advantage of platform-specific optimized implementations, like Sun's Java Advanced Imaging library, but which may not be available in other environments such as J2ME, and vice versa.
The implementation used can be controlled by calling {@link #setGridSampler(GridSampler)} with an instance of a class which implements this interface.
setGridSampler(mixed $newGridSampler) : mixed
Sets the implementation of GridSampler used by the library. One global instance is stored, which may sound problematic. But, the implementation provided ought to be appropriate for the entire platform, and all uses of this library in the whole lifetime of the JVM. For instance, an Android activity can swap in an implementation that takes advantage of native platform libraries.
| mixed | $newGridSampler |
sampleGrid(mixed $image, mixed $dimensionX, mixed $dimensionY, mixed $p1ToX, mixed $p1ToY, mixed $p2ToX, mixed $p2ToY, mixed $p3ToX, mixed $p3ToY, mixed $p4ToX, mixed $p4ToY, mixed $p1FromX, mixed $p1FromY, mixed $p2FromX, mixed $p2FromY, mixed $p3FromX, mixed $p3FromY, mixed $p4FromX, mixed $p4FromY) : mixed
Samples an image for a rectangular matrix of bits of the given dimension. The sampling transformation is determined by the coordinates of 4 points, in the original and transformed image space.
| mixed | $image | |
| mixed | $dimensionX | |
| mixed | $dimensionY | |
| mixed | $p1ToX | |
| mixed | $p1ToY | |
| mixed | $p2ToX | |
| mixed | $p2ToY | |
| mixed | $p3ToX | |
| mixed | $p3ToY | |
| mixed | $p4ToX | |
| mixed | $p4ToY | |
| mixed | $p1FromX | |
| mixed | $p1FromY | |
| mixed | $p2FromX | |
| mixed | $p2FromY | |
| mixed | $p3FromX | |
| mixed | $p3FromY | |
| mixed | $p4FromX | |
| mixed | $p4FromY |
if image can't be sampled, for example, if the transformation defined by the given points is invalid or results in sampling outside the image boundaries
checkAndNudgePoints(mixed $image, mixed $points) : mixed
<p>Checks a set of points that have been transformed to sample points on an image against the image's dimensions to see if the point are even within the image.</p>
This method will actually "nudge" the endpoints back onto the image if they are found to be barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder patterns in an image where the QR Code runs all the way to the image border.
For efficiency, the method will check points from either end of the line until one is found to be within the image. Because the set of points are assumed to be linear, this is valid.
| mixed | $image | |
| mixed | $points |
if an endpoint is lies outside the image boundaries