DrawSkewY oddity in 6.5.4-0

[rmagick]

The following program tries to replicate the SVG "Skew" example here http://www.w3.org/TR/SVG11/coords.html# ... rixDefined, but the X axis in the skewY coordinate system is wrong. Here's the target image:


Here's the output from my test:


Here's the program I used to create the image. Please let me know if you need any more information.

Code: Select all

// gcc `MagickWand-config --cflags --cppflags` -o skew skew.c `MagickWand-config --ldflags --libs`
#include <stdio.h>
#include <stdlib.h>
#include <wand/MagickWand.h>

int main(int argc, char **argv)
{
    MagickWand *wand;
    DrawingWand *drawing;
    PixelWand *none, *white, *black, *red, *blue;

    MagickWandGenesis();

    none = NewPixelWand();
    PixelSetColor(none, "none");
    red = NewPixelWand();
    PixelSetColor(red, "red");
    black = NewPixelWand();
    PixelSetColor(black, "black");
    white = NewPixelWand();
    PixelSetColor(white, "white");
    blue = NewPixelWand();
    PixelSetColor(blue, "blue");

    drawing = NewDrawingWand();

    // Draw the axes of the original coordinate system.
    PushDrawingWand(drawing);
        DrawSetFillColor(drawing, none);
        DrawSetStrokeColor(drawing, black);
        DrawSetStrokeWidth(drawing, 3.0);
        DrawLine(drawing, 0.0, 1.5, 400.0, 1.5);
        DrawLine(drawing, 1.5, 0.0, 1.5, 120.0);
    PopDrawingWand(drawing);

    // Establish a new coordinate system whose origin is at (30,30) in the
    // initial coord. system and which is skewed in X by 30 degrees.
    PushDrawingWand(drawing);
        DrawTranslate(drawing, 30.0, 30.0);
        DrawSkewX(drawing, 30.0);
        PushDrawingWand(drawing);
            DrawSetFillColor(drawing, none);
            DrawSetStrokeColor(drawing, red);
            DrawSetStrokeWidth(drawing, 3.0);
            DrawLine(drawing, 0.0, 0.0, 50.0, 0.0);
            DrawLine(drawing, 0.0, 0.0, 0.0, 50.0);
        PopDrawingWand(drawing);
        PushDrawingWand(drawing);
            DrawSetFontFamily(drawing, "Verdana");
            DrawSetFontSize(drawing, 20.0);
            DrawSetFontWeight(drawing, 400ul);
            DrawSetFontStyle(drawing, NormalStyle);
            DrawSetFillColor(drawing, blue);
            DrawSetStrokeColor(drawing, none);
            DrawAnnotation(drawing, 0.0, 0.0, "ABC (skewX)");
        PopDrawingWand(drawing);
    PopDrawingWand(drawing);

    // Establish a new coordinate system whose origin is at (200, 30) in the
    // initial coord. system and which is skewed in Y by 30 degrees.
    PushDrawingWand(drawing);
        DrawTranslate(drawing, 200.0, 30.0);
        DrawSkewY(drawing, 30.0);
        PushDrawingWand(drawing);
            DrawSetFillColor(drawing, none);
            DrawSetStrokeColor(drawing, red);
            DrawSetStrokeWidth(drawing, 3.0);
            DrawLine(drawing, 0.0, 0.0, 50.0, 0.0);
            DrawLine(drawing, 0.0, 0.0, 0.0, 50.0);
        PopDrawingWand(drawing);
        PushDrawingWand(drawing);
            DrawSetFontFamily(drawing, "Verdana");
            DrawSetFontSize(drawing, 20.0);
            DrawSetFontWeight(drawing, 400ul);
            DrawSetFontStyle(drawing, NormalStyle);
            DrawSetFillColor(drawing, blue);
            DrawSetStrokeColor(drawing, none);
            DrawAnnotation(drawing, 0.0, 0.0, "ABC (skewY)");
        PopDrawingWand(drawing);
    PopDrawingWand(drawing);


    wand = NewMagickWand();
    MagickNewImage(wand, 400, 120, white);
    MagickDrawImage(wand, drawing);
    MagickWriteImage(wand, "Skew.gif");

    DestroyDrawingWand(drawing);
    DestroyMagickWand(wand);
    DestroyPixelWand(none);
    DestroyPixelWand(blue);
    DestroyPixelWand(white);
    DestroyPixelWand(black);
    DestroyPixelWand(red);

    MagickWandTerminus();
}

[magick]

Add

• MagickWriteImage(wand, "Skew.mvg");

after your write to Skew.gif. Now type this command:

• convert msvg:Skew.svg reference.mvg

Now compare Skew.mvg to reference.mvg. The key to success is to get your program to produce essentially the same output as reference.mvg. If you make an effort and can't get it to work, post your progress here and we'll take a closer look at the problem.

[rmagick]

I'll give that a try. Thanks for the tip.

[rmagick]

Here's a simplified version of the skew y problem. Notice that the Y-axis is skewed 60 degrees instead of 30.

Code: Select all

/*
 *  gcc `MagickWand-config --cflags --cppflags` -o skewybug skewybug.c `MagickWand-config --ldflags --libs`
 */
#include <stdio.h>
#include <stdlib.h>
#include <wand/MagickWand.h>

int main(int argc, char **argv)
{
    MagickWand *wand;
    DrawingWand *drawing;
    PixelWand *none, *white, *red;

    MagickWandGenesis();

    none = NewPixelWand();
    PixelSetColor(none, "none");
    red = NewPixelWand();
    PixelSetColor(red, "red");
    white = NewPixelWand();
    PixelSetColor(white, "white");

    drawing = NewDrawingWand();

    DrawTranslate(drawing, 200.0, 30.0);
    DrawSkewY(drawing, 30.0);
    DrawSetStrokeColor(drawing, red);
    DrawSetStrokeWidth(drawing, 3.0);
    DrawLine(drawing, 0.0, 0.0, 50.0, 0.0);
    DrawLine(drawing, 0.0, 0.0, 0.0, 50.0);

    wand = NewMagickWand();
    MagickNewImage(wand, 400, 120, white);
    MagickDrawImage(wand, drawing);
    MagickWriteImage(wand, "skewybug.png");
    MagickWriteImage(wand, "skewybug.mvg");

    DestroyDrawingWand(drawing);
    DestroyMagickWand(wand);
    DestroyPixelWand(none);
    DestroyPixelWand(white);
    DestroyPixelWand(red);

    MagickWandTerminus();
}

Here's the skewybug.mvg file:

Code: Select all

translate 200,30
affine 1,0.57735,0,1,0,0
skewY 30
stroke '#FFFF00000000'
stroke-width 3
line 0,0 50,0
line 0,0 0,50

I notice that manually removing the affine command that DrawSkewY adds fixes the problem.
Here's the skewybug.png file:

[magick]

We can reproduce the problem you reported and have a patch in the Subversion trunk available sometime tomorrow. The patch will also be in the next point release of ImageMagick. Thanks.

[rmagick]

Thanks for both fixes!