我正在使用Cairo中的C编写一个应用程序来执行以下操作：
我遇到的问题是，如果我不旋转方向盘，数字就会正确绘制，如image所示，除非轮子没有根据需要旋转。
但是，如果我尝试旋转并在方向盘上绘制数字，我会得到一个没有数字的旋转滚轮，如image.
所示我尝试了各种代码排列，但我似乎无法使其正常工作。我会很感激一些提示和/或示例代码，以显示我做错了什么。我检查了Cairo文档无济于事。
可以找到代码here.
在这里：
#include <cairo.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
typedef struct
{
int numImages; /* Number of images in win amount string */
int indexes[7]; /* indexes into NumberImages[] */
}WinAmountData;
/***** Function Prototypes *****************/
int InitImages( void );
void DestroyNumberImages( void );
int ParseWinAmountString( char *string, WinAmountData *amtData );
int Rotate( cairo_t *cr , cairo_surface_t *image, double degrees );
/*******************************************/
typedef struct
{
int xOffset; /* pixel count offsete before next digit */
char fileName[20];
cairo_surface_t *image;
}ImageInfo;
ImageInfo NumberImages[] =
{
{ 8, "images/0.png", NULL },
{ 10, "images/1.png", NULL },
{ 10, "images/2.png", NULL },
{ 10, "images/3.png", NULL },
{ 10, "images/4.png", NULL },
{ 10, "images/5.png", NULL },
{ 10, "images/6.png", NULL },
{ 10, "images/7.png", NULL },
{ 10, "images/8.png", NULL },
{ 10, "images/9.png", NULL },
{ 7, "images/$.png", NULL },
{ 10, "images/euro.png", NULL },
{ 7, "images/pound.png", NULL },
{ 7, "images/yen.png", NULL }
};
enum { DOLLAR = 10, EURO, POUND, YEN };
#define FALSE 0
#define TRUE 1
int InitImages( void )
{
int i;
int ret = TRUE;
cairo_status_t imgStatus;
for( i = 0; i < ( sizeof( NumberImages ) / sizeof( ImageInfo ) ) && ret == TRUE; i++ )
{
NumberImages[i].image = cairo_image_surface_create_from_png( NumberImages[i].fileName );
imgStatus = cairo_surface_status(NumberImages[i].image);
ret = ( CAIRO_STATUS_SUCCESS == imgStatus );
}
return( ret );
}
void DestroyNumberImages( void )
{
int i;
for( i = 0; i < ( sizeof( NumberImages ) / sizeof( ImageInfo ) ); i++ )
{
cairo_surface_destroy(NumberImages[i].image);
}
return;
}
int ParseWinAmountString( char *string, WinAmountData *amtData )
{
int ret = TRUE;
int i = 0, len;
len = strlen( string );
if( (len > 0) && (len < 8) )
{
amtData->numImages = len;
for( i = 0; i < amtData->numImages && TRUE == ret; i++ )
{
if( string[i] >= '0' && string[i] <= '9' )
{
amtData->indexes[i] = string[i] - '0';
}
else
{
switch( string[i] )
{
case 'D':
amtData->indexes[i] = DOLLAR;
break;
case 'Y':
amtData->indexes[i] = YEN;
break;
case 'E':
amtData->indexes[i] = EURO;
break;
case 'P':
amtData->indexes[i] = POUND;
break;
default:
ret = FALSE;
break;
}
}
}
}
else
{
ret = FALSE;
}
return( ret );
}
double DegreesToRadians( double degrees )
{
return((double)((double)degrees * ( (double)M_PI/(double)180.0 )));
}
int Rotate( cairo_t *cr , cairo_surface_t *image, double degrees )
{
int ret = 0;
cairo_translate(cr, 90, 90);
cairo_rotate(cr, DegreesToRadians( degrees ));
cairo_set_source_surface(cr, image, -90, -90);
cairo_paint(cr);
return ( ret );
}
int main(int argc, char *argv[])
{
int i,x,y;
cairo_surface_t *imgWheelBg = NULL;
WinAmountData amtData;
if( argc == 2 )
{
printf("Parsing [%s]\n", argv[1]);
if ( ParseWinAmountString( argv[1], &amtData ) == TRUE )
{
printf("Amount indexes = [ ");
for( i = 0; i < amtData.numImages; i++ )
{
printf("%d ", amtData.indexes[i]);
}
printf("]\n");
}
else
{
printf("Failed to parse amount.\n");
return( 1 );
}
}
else
{
printf("Usage: %s <Amount String>\n", argv[0]);
return( 1 );
}
if( InitImages() == TRUE )
{
imgWheelBg = cairo_image_surface_create_from_png("images/blankwheel.png");
//Create the background image
cairo_surface_t *imgResult = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 180, 180);
//Create the cairo context
cairo_t *cr = cairo_create(imgResult);
//Paint empty wheel image
cairo_set_source_surface(cr, imgWheelBg, 0, 0);
cairo_paint(cr);
// At this point the wheel is painted ( blankwheel.png )
// vvvvvvvvvv THIS PART SEEMS TO BE CAUSING TROUBLES vvvvvvvvvv
// With this call the wheel DOES get rotated 90 degress. Confirmed
// by viewing the resulting PNG file.
// HOWEVER, after the Rotate() is called the numbers aren't put on the wheel.
// if I remove the Rotate() call, the wheel is drawn, not rotated, but the
// numbers are properly composited over the image.
//Rotate( cr, imgWheelBg, 90 );
// ^^^^^^^^^^^ THIS PART SEEMS TO BE CAUSING TROUBLES ^^^^^^^^^^^
/* Set drawing begin point in pixels */
x = 101;
y = 82;
/* Draw all characters in win amount string */
for( i = 0; i < amtData.numImages; i++ )
{
cairo_set_source_surface(cr, NumberImages[amtData.indexes[i]].image, x, y);
cairo_paint(cr);
x += NumberImages[i].xOffset;
}
//Destroy the cairo context and/or flush the destination image
cairo_surface_flush(imgResult);
cairo_destroy(cr);
//And write the results into a new file
cairo_surface_write_to_png(imgResult, "result.png");
// Destroy resources
cairo_surface_destroy(imgResult);
cairo_surface_destroy(imgWheelBg);
DestroyNumberImages();
printf("SUCCESS\n");
}
else
{
printf("FAILED Init Images\n");
}
return 0;
}
编辑：最终目标是以编程方式生成图像like this one，并根据需要在GTK应用程序中实时生成动画。
编辑：根据Mikhail Kozhevnikov和Uli Schlachter的评论，我能够使用this code找到解决方案。
非常感谢！
答案 0 :(得分：1)
我认为问题在于转换应用于所有事物，包括数字图像，并且由于这种转换，它们被绘制在图片之外的某处。在应用转换之前我建议the matrix be stored，在绘制圆之后建议restored。或者你想要旋转数字吗？..
