#include <u.h> #include <libc.h> #include <draw.h>
Image *allocimage(Display *d, Rectangle r,
ulong chan, int repl, int col)
Image *allocimagemix(Display *d, ulong one, ulong three)
void freeimage(Image *i)
int nameimage(Image *i, char *name, int in)
Image *namedimage(Display *d, char *name)
ulong setalpha(ulong color, uchar alpha)
int loadimage(Image *i, Rectangle r, uchar *data, int ndata)
int cloadimage(Image *i, Rectangle r, uchar *data, int ndata)
int unloadimage(Image *i, Rectangle r, uchar *data, int ndata)
Image *readimage(Display *d, int fd, int dolock)
int writeimage(int fd, Image *i, int dolock)
int bytesperline(Rectangle r, int d)
int wordsperline(Rectangle r, int d)
enum{ DOpaque = 0xFFFFFFFF, DTransparent = 0x00000000, DBlack = 0x000000FF, DWhite = 0xFFFFFFFF, DRed = 0xFF0000FF, DGreen = 0x00FF00FF, DBlue = 0x0000FFFF, DCyan = 0x00FFFFFF, DMagenta = 0xFF00FFFF, DYellow = 0xFFFF00FF, DPaleyellow = 0xFFFFAAFF, DDarkyellow = 0xEEEE9EFF, DDarkgreen = 0x448844FF, DPalegreen = 0xAAFFAAFF, DMedgreen = 0x88CC88FF, DDarkblue = 0x000055FF, DPalebluegreen = 0xAAFFFFFF, DPaleblue = 0x0000BBFF, DBluegreen = 0x008888FF, DGreygreen = 0x55AAAAFF, DPalegreygreen = 0x9EEEEEFF, DYellowgreen = 0x99994CFF, DMedblue = 0x000099FF, DGreyblue = 0x005DBBFF, DPalegreyblue = 0x4993DDFF, DPurpleblue = 0x8888CCFF, DNotacolor = 0xFFFFFF00, DNofill = DNotacolor, };DESCRIPTIONA new Image on Display d is allocated with allocimage ; it will have the rectangle, pixel channel format, and replication flag given by its arguments. Convenient pixel channels like GREY1 , GREY2 , CMAP8 , RGB16 , RGB24 , and RGBA32 are predefined. All the new image's pixels will have initial value col . If col is DNofill , no initialization is done. Representative useful values of color are predefined: DBlack , DWhite , DRed , and so on. Colors are specified by 32-bit numbers comprising, from most to least significant byte, 8-bit values for red, green, blue, and alpha. The values correspond to illumination, so 0 is black and 255 is white. Similarly, for alpha 0 is transparent and 255 is opaque. The id field will have been set to the identifying number used by /dev/draw (see draw (3)), and the cache field will be zero. If repl is true, the clip rectangle is set to a very large region; if false, it is set to r . The depth field will be set to the number of bits per pixel specified by the channel descriptor (see image (6)). Allocimage returns 0 if the server has run out of image memory.Allocimagemix is used to allocate background colors. On 8-bit color-mapped displays, it returns a 2×2 replicated image with one pixel colored the color one and the other three with three . (This simulates a wider range of tones than can be represented by a single pixel value on a color-mapped display.) On true color displays, it returns a 1×1 replicated image whose pixel is the result of mixing the two colors in a one to three ratio.
Freeimage frees the resources used by its argument image.
Nameimage publishes in the server the image i under the given name . If in is non-zero, the image is published; otherwise i must be already named name and it is withdrawn from publication. Namedimage returns a reference to the image published under the given name on Display d . These routines permit unrelated applications sharing a display to share an image; for example they provide the mechanism behind getwindow (see graphics (2)).
The RGB values in a color are premultiplied by the alpha value; for example, a 50% red is 0x7F00007F not 0xFF00007F . The function setalpha performs the alpha computation on a given color , ignoring its initial alpha value, multiplying the components by the supplied alpha . For example, to make a 50% red color value, one could execute setalpha(DRed, 0x7F) .
The remaining functions deal with moving groups of pixel values between image and user space or external files. There is a fixed format for the exchange and storage of image data (see image (6)).
Unloadimage reads a rectangle of pixels from image i into data , whose length is specified by ndata . It is an error if ndata is too small to accommodate the pixels.
Loadimage replaces the specified rectangle in image i with the ndata bytes of data .
The pixels are presented one horizontal line at a time, starting with the top-left pixel of r . In the data processed by these routines, each scan line starts with a new byte in the array, leaving the last byte of the previous line partially empty, if necessary. Pixels are packed as tightly as possible within data , regardless of the rectangle being extracted. Bytes are filled from most to least significant bit order, as the x coordinate increases, aligned so x =0 would appear as the leftmost pixel of its byte. Thus, for depth 1, the pixel at x offset 165 within the rectangle will be in a data byte at bit-position 0x04 regardless of the overall rectangle: 165 mod 8 equals 5, and "0x80 >> 5" equals 0x04 .
Cloadimage does the same as loadimage , but for ndata bytes of compressed image data (see image (6)). On each call to cloadimage, the data must be at the beginning of a compressed data block, in particular, it should start with the y coordinate and data length for the block.
Loadimage , cloadimage , and unloadimage return the number of bytes copied.
Readimage creates an image from data contained in an external file (see image (6) for the file format); fd is a file descriptor obtained by opening such a file for reading. The returned image is allocated using allocimage . The dolock flag specifies whether the Display should be synchronized for multithreaded access; single-threaded programs can leave it zero.
Writeimage writes image i onto file descriptor fd , which should be open for writing. The format is as described for readimage .
Readimage and writeimage do not close fd .
Bytesperline and wordsperline return the number of bytes or words occupied in memory by one scan line of rectangle r in an image with d bits per pixel.
EXAMPLETo allocate a single-pixel replicated image that may be used to paint a region red, .EX red = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, DRed);SOURCE/sys/src/libdraw"SEE ALSO"graphics (2), draw (2), draw (3), image (6)DIAGNOSTICSThese functions return pointer 0 or integer -1 on failure, usually due to insufficient memory.May set errstr .
BUGSDepth must be a divisor or multiple of 8.