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Index ¶
- Constants
- func CustomSimilar(iconA, iconB IconT, coeff CustomCoefficients) bool
- func CustomSimilar90270(iconA, iconB IconT, coeff CustomCoefficients) bool
- func DefaultThresholds()
- func EucMetric(iconA, iconB IconT) (m1, m2, m3 float64)
- func Get(icon IconT, size int, p image.Point) (c1, c2, c3 float64)
- func Open(path string) (img image.Image, err error)
- func PropMetric(iconA, iconB IconT) (m float64)
- func ResizeByNearest(src image.Image, dstSize image.Point) (dst image.RGBA, srcSize image.Point)
- func SaveToJPG(img *image.RGBA, path string, quality int)
- func SaveToPNG(img *image.RGBA, path string)
- func Set(icon IconT, size int, p image.Point, c1, c2, c3 float64)
- func Similar(iconA, iconB IconT) bool
- func Similar90270(iconA, iconB IconT) bool
- type CustomCoefficients
- type IconT
Constants ¶
const ( // Image resolution of the icon is very small // (11x11 pixels), therefore original image details // are lost in downsampling, except when source images // have very low resolution (e.g. favicons or simple // logos). This is useful from the privacy perspective // if you are to use generated icons in a large searchable // database. IconSize = 11 // Exported to be used in package imagehash. )
Variables ¶
This section is empty.
Functions ¶
func CustomSimilar ¶
func CustomSimilar(iconA, iconB IconT, coeff CustomCoefficients) bool
CustomSimilar is like Similar, except it allows changing default thresholds by multiplying them. The practically useful range of the coefficients is [0, 1.0), but can be equal or larger than 1 if necessary. All coefficients set to 0 correspond to identical images, for example an image file copy. All coefficients equal to 1 make func CustomSimilar equivalent to func Similar.
func CustomSimilar90270 ¶
func CustomSimilar90270(iconA, iconB IconT, coeff CustomCoefficients) bool
Similar90270 works like Similar, but also considers rotations of ±90°. Those are rotations users might reasonably often do.
func EucMetric ¶
EucMetric returns Euclidean distances between 2 icons. These are 3 metrics corresponding to each color channel. Distances are squared, not to waste CPU on square root calculations. Note: color channels of icons are YCbCr (not RGB).
func Get ¶
Get reads pixel values in an icon at a point. c1, c2, c3 are color values for each channel (RGB for example). Exported to be used in package imagehash.
func PropMetric ¶
PropMetric gives image proportion similarity metric for image A and B. The smaller the metric the more similar are images by their x-y size.
func ResizeByNearest ¶
ResizeByNearest resizes an image to the destination size with the nearest neighbour method. It also returns the source image size.
func Set ¶
Set places pixel values in an icon at a point. c1, c2, c3 are color values for each channel (RGB for example). Size is icon size. Exported to be used in package imagehash.
func Similar90270 ¶
Similar90270 works like Similar, but also considers rotations of ±90°. Those are rotations users might reasonably often do.
Types ¶
type CustomCoefficients ¶
type CustomCoefficients struct {
Y float64 // Luma (grayscale information).
Cb float64 // Chrominance b (color information).
Cr float64 // Chrominance r (color information).
Prop float64 // Proportion tolerance (how similar are image borders).
}
Threshold multiplication coefficients for func CustomSimilar. When all values equal 1.0 func CustomSimilar is equivalent to func Similar. By setting those values less than 1, similarity comparison becomes stricter (more precise). Values larger than 1 will generalize more and show more false positives. When uncertain, setting all coefficients to 1.0 is the safe starting point.
type IconT ¶
type IconT struct {
Pixels []uint16 // Visual signature.
ImgSize image.Point // Original image size.
}
Icon has square shape. Its pixels are uint16 values in 3 channels. uint16 is intentional to preserve color relationships from the full-size image. It is a 255- premultiplied color value in [0, 255] range.
func EmptyIcon ¶
func EmptyIcon() (icon IconT)
EmptyIcon is an icon constructor in case you need an icon with nil values, for example for convenient error handling. Then you can use icon.Pixels == nil condition.
func Icon ¶
Icon generates a normalized image signature ("icon"). Generated icons can then be stored in a database and used for comparison. Icon is the recommended function, vs less robust func IconNN.
func IconNN ¶
IconNN generates a NON-normalized image signature (icon). Icons made with IconNN can be used instead of icons made with func Icon, but mostly for experimental purposes, allowing better understand how the algorithm works, or performing less agressive customized normalization. Not for general use.
Source Files