Blep.TextureOps

Blep.TextureOps is a Unity plugin that allows you to manipulate Textures using compute shaders. Highlights include an O(n) gaussian blur, affine and perspective warps, and photoshop blends, It can be used as a lightweight alternative to OpenCV Note: This has been tested on OSX/Metal and Windows/DirectX, but should work on all platforms that support compute shaders. If there are problems, please let me know.

A static class provides all the functionality, for example:

• TextureOps.Add(srcA, srcB, dst)
• TextureOps.Threshold(src, dst, 0.5f)
• TextureOps.Circle(src, Color.red, float2(100, 100), 10)

See more examples in TextureOpsExample.cs.

The TextureCompute class provides some nice utilities for working with Textures and compute shaders so you can write your own operations.

Installation Instructions

Install from Git or copy to your Assets folder

Supported Operations

Note: many of these can work in-place.

Math

Copy	Dst = Src
Clear	Dst = 0
Set	Dst = Constant
Set	Dst = lerp(Dst, Constant, ChannelMask)
Set	Dst = lerp(Dst, Constant, ImageMask)
Invert	Dst = 1 - Src
Add	Dst = Src + Constant
Add	Dst = SrcA + SrcB
Multiply	Dst = Src * Constant
Multiply	Dst = SrcA * SrcB
MultiplyAdd	Dst = Src * ConstantA + ConstantB
AddWeighted	Dst = SrcA * ConstantA + SrcB * ConstantB
Lerp	Dst = lerp(SrcA, SrcB, Constant)
Clamp	Dst = clamp(Src, ConstantA, ConstantB)
Min	Dst = min(SrcA, SrcB)
Max	Dst = max(SrcA, SrcB)
Saturate	Dst = saturate(Src)
Remap	Dst = remap(Src, fromMin, fromMax, toMin, toMax)

Drawing

Circle	Draw a circle with an optional outline.
Ellipse	Draw an ellipse with an optional outline.
Rectangle	Draw a rectangle with an optional outline.
Line	Draw a line with an optional outline.

Image Processing

Simple

Grayscale	Convert to grayscale.
GrayscaleGamma	Convert a gamma image to grayscale.
ConvertRGB2HSV	Convert RGB to HSV.
ConvertHSV2RGB	Convert HSV to RGB.
Swizzle	Swizzle an image's channels.
Lookup	Lookup using a pallete.
Contrast	Adjust image contrast.
Threshold	Threshold an image.

Morphology Etc

Erode	Erode an image.
Dilate	Dilate an image.
Skeletonize	Skeletonize an image.
DistanceTransform	Compute distance to closest non-zero pixel.

Convolution

BlurGaussian	Blur image with a Gaussian kernel.
BlurGaussianRecursive	Blur image with fast O(n) algorithm. Imprecise for small blurs.
Bilateral	Bilateral-filter an image.
Median3x3	Median-filter an image with a 3x3 neighborhood.
Median5x5	Median-filter an image with a 5x5 neighborhood.
Sobel	Detect edges with a Sobel filter.
Scharr	Detect edges with a Scharr filter.

Stats

GetHistogram	Calculate and return image histogram.
EqualizeHistogram	Equalize image histogram.
Reduce	Used by MinValue, MaxValue, and AverageValue.
MinValue	Return minimum pixel value.
MaxValue	Return maximum pixel value.
AverageValue	Return average pixel value.

Composition

ComposeOver	SrcA appears on top of SrcB, blending them based on their alpha channels.
ComposeIn	SrcB acts as a matte for SrcA. SrcA shows only where SrcB is visible.
ComposeOut	SrcB acts as a inverse matte for SrcA. SrcA shows only where SrcB is not visible.
ComposeAtop	SrcA is drawn on top of SrcB, but only where SrcB is not transparent.
ComposeXor	SrcA and SrcB mutually exclude each other. Where they overlap, the result is transparent.
ComposePlus	Adds SrcA and SrcB together; used for additive blending.

Blend

These are based on Photoshop blend modes.

BlendColorBurn	Looks at the color information in each channel and darkens the base color to reflect the blend color by increasing the contrast between the two.
BlendLinearBurn	Looks at the color information in each channel and darkens the base color to reflect the blend color by decreasing the brightness.
BlendScreen	Looks at each channel’s color information and multiplies the inverse of the blend and base colors.
BlendColorDodge	Looks at the color information in each channel and brightens the base color to reflect the blend color by decreasing contrast between the two.
BlendLinearDodge	Looks at the color information in each channel and brightens the base color to reflect the blend color by decreasing contrast between the two.
BlendOverlay	Multiplies or screens the colors, depending on the base color.
BlendSoftLight	Darkens or lightens the colors, depending on the blend color.
BlendHardLight	Multiplies or screens the colors, depending on the blend color.
BlendVividLight	Burns or dodges the colors by increasing or decreasing the contrast, depending on the blend color.
BlendLinearLight	Burns or dodges the colors by decreasing or increasing the brightness, depending on the blend color.
BlendPinLight	Replaces the colorsI, depending on the blend color.

Geometric Transformations

Note: Warp functions take an inverse matrix.

FlipHorizontal	Flip an image horizontally.
FlipVertical	Flip an image vertically.
Rotate180	Rotate an image by 180 (flip both horizontally and vertically).
WarpAffine	Warp an image by an affine transformation
WarpPerspective	Warp an image by an perspective transformation

Helper methods

GetInverseAffineMatrix	Creates an inverse matrix from a scale, rotation, and translation
GetInverseCornerWarpMatrix	Creates an inverse matrix from a four-corner warp

Known Limitations

• Does minimal parameter checking, for example making sure that the dimensions of the images in a binary operation are the same size.

License

See LICENSE.md and COPYRIGHT.md