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我使用libpng生成png文件。對於RGB png,沒有問題。但我想給png一個透明的屬性。如何讓png具有透明屬性
我參考一些代碼,並添加地方使用*到已檢舉
* 行++ = 230; * PNG_COLOR_TYPE_RGBA,*
,使其具有透明特性, 代碼成功地運行,但餘did't看到透明效果。
任何熟悉libpng或png操作的人都能幫助我嗎?
在此代碼中, 其中pixel_t,& bitmap_t是一些帶有rgb數據的數據。
/* A colored pixel. */
typedef struct {
uint8_t red;
uint8_t green;
uint8_t blue;
} pixel_t;
/* A picture. */
typedef struct {
pixel_t *pixels;
size_t width;
size_t height;
} bitmap_t;
static int save_png_to_file (bitmap_t *bitmap, const char *path)
{
FILE * fp;
png_structp png_ptr = NULL;
png_infop info_ptr = NULL;
size_t x, y;
png_byte ** row_pointers = NULL;
/* "status" contains the return value of this function. At first
it is set to a value which means 'failure'. When the routine
has finished its work, it is set to a value which means
'success'. */
int status = -1;
/* The following number is set by trial and error only. I cannot
see where it it is documented in the libpng manual.
*/
int pixel_size = 3;
int depth = 8;
fp = fopen (path, "wb");
if (! fp) {
goto fopen_failed;
}
png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (png_ptr == NULL) {
goto png_create_write_struct_failed;
}
info_ptr = png_create_info_struct (png_ptr);
if (info_ptr == NULL) {
goto png_create_info_struct_failed;
}
// png_set_invert_alpha(png_ptr);
/* Set up error handling. */
if (setjmp (png_jmpbuf (png_ptr))) {
goto png_failure;
}
/* Set image attributes. */
png_set_IHDR (png_ptr,
info_ptr,
bitmap->width,
bitmap->height,
depth,
*PNG_COLOR_TYPE_RGBA,*
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
/* Initialize rows of PNG. */
//(png_byte **) added by li
row_pointers = (png_byte **)png_malloc (png_ptr, bitmap->height * sizeof (png_byte *));
for (y = 0; y < bitmap->height; ++y) {
//png_byte * added by li
// png_byte *row = (png_byte *)
// png_malloc (png_ptr, sizeof (uint8_t) * bitmap->width * pixel_size);
png_byte *row = (png_byte *)
png_malloc (png_ptr, sizeof (uint8_t) * bitmap->width * 4);
row_pointers[y] = row;
for (x = 0; x < bitmap->width; ++x) {
pixel_t * pixel = pixel_at (bitmap, x, y);
*row++ = pixel->red;
*row++ = pixel->green;
*row++ = pixel->blue;
**row++ = 230;*
}
}
/* Write the image data to "fp". */
png_init_io (png_ptr, fp);
png_set_rows (png_ptr, info_ptr, row_pointers);
png_write_png (png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
/* The routine has successfully written the file, so we set
"status" to a value which indicates success. */
status = 0;
for (y = 0; y < bitmap->height; y++) {
png_free (png_ptr, row_pointers[y]);
}
png_free (png_ptr, row_pointers);
png_failure:
png_create_info_struct_failed:
png_destroy_write_struct (&png_ptr, &info_ptr);
png_create_write_struct_failed:
fclose (fp);
fopen_failed:
return status;
}
你有任何即時消息的東西?我有一些問題,但需要顯示照片 – user1279988
@ user1279988我的電子郵件是在我的個人資料 – leonbloy
對不起。你可以選擇別人看不到你的電子郵件帳戶。我看不到它。它是從您的pngj項目所有者帳戶[email protected]中挖掘出來的,謝謝 – user1279988