I am reading the php documentation for the function imagecreatetruecolor
, which returns an image resource identifier on success. What does it mean by "image resource identifier"? I searched the PHP documentation for this term but did not find it in the first two pages of documentation.
It's basically just a special type of object for use with the gdlib
- other functions will require this resource as a parameter such as imagecolorallocate
.
It stores the information about the image you're creating for further modification with other functions later on.
A little bit of info on resources from php.net here
image resource identifier is a structure (in C terms) defined to hold the information about the image. Here is its definition in PHP sources code:
typedef struct gdImageStruct {
/* Palette-based image pixels */
unsigned char ** pixels;
int sx;
int sy;
/* These are valid in palette images only. See also
'alpha', which appears later in the structure to
preserve binary backwards compatibility */
int colorsTotal;
int red[gdMaxColors];
int green[gdMaxColors];
int blue[gdMaxColors];
int open[gdMaxColors];
/* For backwards compatibility, this is set to the
first palette entry with 100% transparency,
and is also set and reset by the
gdImageColorTransparent function. Newer
applications can allocate palette entries
with any desired level of transparency; however,
bear in mind that many viewers, notably
many web browsers, fail to implement
full alpha channel for PNG and provide
support for full opacity or transparency only. */
int transparent;
int *polyInts;
int polyAllocated;
struct gdImageStruct *brush;
struct gdImageStruct *tile;
int brushColorMap[gdMaxColors];
int tileColorMap[gdMaxColors];
int styleLength;
int stylePos;
int *style;
int interlace;
/* New in 2.0: thickness of line. Initialized to 1. */
int thick;
/* New in 2.0: alpha channel for palettes. Note that only
Macintosh Internet Explorer and (possibly) Netscape 6
really support multiple levels of transparency in
palettes, to my knowledge, as of 2/15/01. Most
common browsers will display 100% opaque and
100% transparent correctly, and do something
unpredictable and/or undesirable for levels
in between. TBB */
int alpha[gdMaxColors];
/* Truecolor flag and pixels. New 2.0 fields appear here at the
end to minimize breakage of existing object code. */
int trueColor;
int ** tpixels;
/* Should alpha channel be copied, or applied, each time a
pixel is drawn? This applies to truecolor images only.
No attempt is made to alpha-blend in palette images,
even if semitransparent palette entries exist.
To do that, build your image as a truecolor image,
then quantize down to 8 bits. */
int alphaBlendingFlag;
/* Should antialias functions be used */
int antialias;
/* Should the alpha channel of the image be saved? This affects
PNG at the moment; other future formats may also
have that capability. JPEG doesn't. */
int saveAlphaFlag;
/* 2.0.12: anti-aliased globals */
int AA;
int AA_color;
int AA_dont_blend;
unsigned char **AA_opacity;
int AA_polygon;
/* Stored and pre-computed variables for determining the perpendicular
* distance from a point to the anti-aliased line being drawn:
*/
int AAL_x1;
int AAL_y1;
int AAL_x2;
int AAL_y2;
int AAL_Bx_Ax;
int AAL_By_Ay;
int AAL_LAB_2;
float AAL_LAB;
/* 2.0.12: simple clipping rectangle. These values must be checked for safety when set; please use gdImageSetClip */
int cx1;
int cy1;
int cx2;
int cy2;
gdInterpolationMethod interpolation_id;
interpolation_method interpolation;
} gdImage;
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