Attachment 7893 Details for Bug 9148 – Test case showing error

Test case showing error

cairo_scale_bug.c (text/plain), 2.83 KB, created by Ed Swartz on 2006-11-24 13:45:20 UTC

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Creator: Ed Swartz

Created: 2006-11-24 13:45:20 UTC

Size: 2.83 KB

patch

obsolete

>/**
> *	This test shows that soemthing foul is afoot when a large 
> *	source surface is scaled down and painted onto a smaller target surface.
> *
> * 	Scaling is applied so that the same effective image should
> *	result no matter how large the source surface is, but this test
> *	shows that is not the case.
> *
> */
>
>#include <cairo.h>
>#include <stdio.h>
>
>int surface_size;
>int image_size;
>
>void clear(cairo_surface_t* surface)
>{
>	cairo_t* ctx = cairo_create(surface);
>	cairo_set_operator(ctx, CAIRO_OPERATOR_CLEAR);
>	cairo_fill(ctx);
>
>	cairo_set_operator(ctx, CAIRO_OPERATOR_OVER);
>	cairo_set_source_rgb(ctx, 0, 0, 0);
>	cairo_rectangle(ctx, 0, 0, surface_size, surface_size);
>	cairo_stroke(ctx);
>	cairo_destroy(ctx);
>}
>
>void show_matrix(cairo_t* ctx)
>{
>	cairo_matrix_t mtx;
>	cairo_get_matrix(ctx, &mtx);
>	printf("matrix: %g %g %g %g %g %g\n",
>		   mtx.xx, mtx.yx, mtx.xy, mtx.yy, mtx.x0, mtx.y0);
>}
>
>void draw1(cairo_surface_t* surface, cairo_surface_t* image)
>{
>	clear(surface);
>
>	cairo_t* ctx = cairo_create(surface);
>	cairo_set_source_rgb(ctx, 0, 0, 0);
>	cairo_rectangle(ctx, 0, 0, surface_size, surface_size);
>	cairo_stroke(ctx);
>
>	int end_size = 16;
>	double scale = (double)end_size / image_size;
>
>	// drawing on the upper left is fine
>	cairo_identity_matrix(ctx);
>	cairo_translate(ctx, 0, 0);
>	cairo_scale(ctx, scale, scale);
>	cairo_set_source_surface(ctx, image, 0, 0);
>	show_matrix(ctx);
>	cairo_paint(ctx);
>
>	// drawing on the lower right results in problems
>	cairo_identity_matrix(ctx);
>	cairo_translate(ctx, surface_size - end_size, surface_size - end_size);
>	cairo_scale(ctx, scale, scale);
>	cairo_set_source_surface(ctx, image, 0, 0);
>	show_matrix(ctx);
>	cairo_paint(ctx);
>
>	{
>		char filename[256];
>		snprintf(filename, sizeof(filename), "test_%04d.png", image_size);
>		cairo_surface_write_to_png(surface, filename);
>	}
>
>	cairo_destroy(ctx);
>
>}
>
>void run_round()
>{
>
>	cairo_surface_t* surface = cairo_image_surface_create(
>		CAIRO_FORMAT_ARGB32, surface_size, surface_size);
>	cairo_surface_t* image = cairo_image_surface_create(
>		CAIRO_FORMAT_ARGB32, image_size, image_size);
>
>	// get green & red check pattern
>	cairo_t* ctx = cairo_create(image);
>	cairo_set_source_rgb(ctx, 1, 0, 0);
>	cairo_rectangle(ctx, 0, 0, image_size / 2, image_size / 2);
>	cairo_fill(ctx);
>	cairo_set_source_rgb(ctx, 0, 1, 0);
>	cairo_rectangle(ctx, image_size / 2, image_size / 2, image_size / 2, image_size / 2);
>	cairo_fill(ctx);
>	cairo_destroy(ctx);
>
>	draw1(surface, image);
>	//draw2(surface,image);
>
>	cairo_surface_destroy(surface);
>	cairo_surface_destroy(image);
>
>}
>
>int main(void) 
>{
>	surface_size = 512;
>
>	image_size = 128;
>	run_round();
>
>	image_size = 1024;
>	run_round();
>
>	// at these sizes, the image progressively disappears
>	// in a strange direction
>	image_size = 1060;
>	run_round();
>	image_size = 1065;
>	run_round();
>	image_size = 1070;
>	run_round();
>	image_size = 2048;
>	run_round();
>
>	return 0;
>}

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