Available in LEADTOOLS Imaging Pro, Vector, Document, and Medical Imaging toolkits. |
#include "l_bitmap.h"
L_LTFIL_API L_UINT L_GetPNGTRNS (pData)
L_UCHAR *pData; |
/* pointer to a buffer */ |
Gets the transparency data used by LEADTOOLS when loading PNG files.
Parameter |
Description |
pData |
Pointer to a buffer to be updated with the transparency data used when loading PNG files. |
Returns
0 or > 1 |
The length of the data buffer. |
< 1 |
An error occurred. Refer to Return Codes. |
Comments
This function supports1-bit to 8-bit PNG images.
To set the transparency data used when saving PNG files, use L_SetPNGTRNS function.
The transparency data obtained by this function is valid for the current thread.
Required DLLs and Libraries
LTFIL For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application. |
Platforms
Win32, x64.
See Also
Functions: |
L_SetPNGTRNS, L_SetBitmapAlpha, L_CreateMaskFromBitmapRgn, L_SetBitmapRgnFromMask |
Topics: |
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Example
//This example gets PNG transparency data
#define MAKE_IMAGE_PATH(pFileName) TEXT("C:\\Users\\Public\\Documents\\LEADTOOLS Images\\")pFileName L_INT GetPNGTRNSExample(L_VOID) { L_INT nRet; BITMAPHANDLE Bitmap; // Load an image with or without transparency nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("LittleGFlyingAlpha.png")), &Bitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGRORGRAY, NULL, NULL); if( nRet != SUCCESS) return nRet; Bitmap.Flags.Transparency = TRUE; //Get the PNG transparency data L_UCHAR* pData = NULL; //Allocate memory for the transparency data buffer pData = (L_UCHAR *)malloc(256 * sizeof(L_UCHAR)); memset(pData, 0, 256 * sizeof(L_UCHAR)); // This will likely return 0 if we loaded an image without transparency nRet = L_GetPNGTRNS(pData); if(nRet == 0) { OutputDebugString(L_TEXT("No transparencey found!\n")); } //print out the transparency loaded from PNG L_TCHAR msg[200] = L_TEXT(""); for (int i = 0; i < 256; i++) { wsprintf(msg, L_TEXT("pData[%d]: %d\t"), i, pData[i]); OutputDebugString(msg); if (((i+1)%4) == 0) OutputDebugString(L_TEXT("\n")); } //print out the palette for (int i = 0; i < 256; i++) { wsprintf(msg, L_TEXT("pPalette[%d]: %d\t"), i, Bitmap.pPalette[i]); OutputDebugString(msg); if (((i+1)%4) == 0) OutputDebugString(L_TEXT("\n")); } //change the alpha values and print out for (int i = 0; i < 256; i+=4) { // every four colors are 100%, 75%, 50%, and 0% transparent pData[i] = 0; pData[i + 1] = 64; pData[i + 2] = 128; pData[i + 3] = 255; wsprintf(msg, L_TEXT("pData[%d]: %d\tpData[%d]: %d\tpData[%d]: %d\tpData[%d]: %d\t\n"), i, pData[i], i + 1, pData[i + 1], i + 2, pData[i + 2], i + 3, pData[i + 3]); OutputDebugString(msg); if (((i+1)%4) == 0) OutputDebugString(L_TEXT("\n")); } // Set the transparency data and save the file nRet = L_SetPNGTRNS(pData, 256); free(pData); if(nRet != SUCCESS) { L_FreeBitmap(&Bitmap); return nRet; } nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("output.png")), &Bitmap, FILE_PNG, 8, 0, NULL); L_FreeBitmap(&Bitmap); return nRet; }