fortplot_rendering_comparison Module

Enhanced rendering comparison framework for detecting visual regressions

This module provides systematic comparison tools for PNG/PDF outputs to identify specific rendering differences between commits or versions.

= Key Features = - Pixel-level difference analysis for raster formats - Statistical similarity metrics (MSE, SSIM, histogram comparison) - Visual similarity assessment using perceptual models - Performance optimization for large image comparisons - Comprehensive test coverage for regression detection

= Comparison Modes = - PIXEL_DIFF: Direct pixel-by-pixel comparison - STATISTICAL: Mean squared error and correlation analysis - HISTOGRAM: Color distribution comparison - PERCEPTUAL: Human-vision-weighted similarity metrics

= Usage Examples = ! Basic pixel difference result = compare_png_images("reference.png", "current.png", PIXEL_DIFF)

! Statistical analysis with threshold result = compare_with_threshold("ref.png", "test.png", 0.95_wp)

! Batch comparison for regression testing call run_regression_suite("reference_dir/", "current_dir/", results)

Derived Types

type, public ::  comparison_mode_t

Components

Type	Visibility	Attributes		Name		Initial
integer,	public		::	mode

type, public ::  comparison_result_t

Components

Type	Visibility	Attributes		Name		Initial
logical,	public		::	passed
character(len=512),	public		::	message
real(kind=wp),	public		::	similarity_score
real(kind=wp),	public		::	mse_value
real(kind=wp),	public		::	ssim_value
real(kind=wp),	public		::	histogram_correlation
integer,	public		::	different_pixels
integer,	public		::	total_pixels
type(comparison_mode_t),	public		::	mode_used

Functions

public function compare_png_images(reference_path, current_path, mode) result(comparison)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_path
character(len=*),	intent(in)			::	current_path
type(comparison_mode_t),	intent(in)			::	mode

Return Value type(comparison_result_t)

public function compare_pdf_files(reference_path, current_path) result(comparison)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_path
character(len=*),	intent(in)			::	current_path

Return Value type(comparison_result_t)

public function compare_with_threshold(reference_path, current_path, threshold) result(comparison)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_path
character(len=*),	intent(in)			::	current_path
real(kind=wp),	intent(in)			::	threshold

Return Value type(comparison_result_t)

public function calculate_similarity_metrics(reference_path, current_path) result(metrics)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_path
character(len=*),	intent(in)			::	current_path

Return Value type(comparison_result_t)

public function optimize_comparison_performance(width, height, mode) result(should_optimize)

Arguments

Type	Intent	Optional	Attributes		Name
integer,	intent(in)			::	width
integer,	intent(in)			::	height
type(comparison_mode_t),	intent(in)			::	mode

Return Value logical

Subroutines

public subroutine run_regression_suite(reference_dir, current_dir, results)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_dir
character(len=*),	intent(in)			::	current_dir
type(comparison_result_t),	intent(out),		allocatable	::	results(:)

public subroutine generate_diff_image(reference_path, current_path, diff_output_path)

Arguments

Type	Intent	Optional	Attributes		Name
character(len=*),	intent(in)			::	reference_path
character(len=*),	intent(in)			::	current_path
character(len=*),	intent(in)			::	diff_output_path