Skip to main content

Relational

Comparison and relational operations on images.

Function Mapping​

libvips CDart BindingDescription
vips_relational()relationalBindings.relational()General relational operation
vips_equal()relationalBindings.equal()Test equality
vips_notequal()relationalBindings.notequal()Test inequality
vips_less()relationalBindings.less()Test less than
vips_lesseq()relationalBindings.lesseq()Test less than or equal
vips_more()relationalBindings.more()Test greater than
vips_moreeq()relationalBindings.moreeq()Test greater than or equal
vips_relational_const()relationalBindings.relationalConst()Compare with constant
vips_equal_const()relationalBindings.equalConst()Test equality with constant
vips_boolean()relationalBindings.boolean()Boolean operation
vips_andimage()relationalBindings.andimage()Bitwise AND
vips_orimage()relationalBindings.orimage()Bitwise OR
vips_eorimage()relationalBindings.eorimage()Bitwise XOR

relational​

General relational comparison between two images.

relationalBindings.relational(image1, image2, output, VipsOperationRelational.equal);

Operations (VipsOperationRelational):

  • equal - Test equality
  • notequal - Test inequality
  • less - Test less than
  • lesseq - Test less than or equal
  • more - Test greater than
  • moreeq - Test greater than or equal

equal / notequal​

Test pixel-wise equality.

// Compare two images
relationalBindings.equal(image1, image2, output);
relationalBindings.notequal(image1, image2, output);

Result: 255 where condition is true, 0 where false.

less / lesseq / more / moreeq​

Pixel-wise comparison.

relationalBindings.less(image1, image2, output);     // image1 < image2
relationalBindings.lesseq(image1, image2, output);   // image1 <= image2
relationalBindings.more(image1, image2, output);     // image1 > image2
relationalBindings.moreeq(image1, image2, output);   // image1 >= image2

relational_const​

Compare image with a constant value.

relationalBindings.equalConst(image, output, 128);   // pixels == 128
relationalBindings.moreConst(image, output, 128);    // pixels > 128

boolean​

Bitwise boolean operations.

relationalBindings.andimage(image1, image2, output);  // Bitwise AND
relationalBindings.orimage(image1, image2, output);   // Bitwise OR
relationalBindings.eorimage(image1, image2, output);  // Bitwise XOR

Use Cases​

Thresholding​

// Create binary mask where pixels > 128
relationalBindings.moreConst(image, mask, 128);

Image Masking​

// Apply mask: keep pixels where mask is 255
relationalBindings.andimage(image, mask, output);

Difference Detection​

// Find pixels that differ between two images
relationalBindings.notequal(image1, image2, diff);