Port variable image resolution support from libgd 2.1.0

The PHP binding for this feature will be submitted as a separate PR.

Author: cmb69

ext/gd/libgd/gd.c

@@ -170,6 +170,8 @@ gdImagePtr gdImageCreate (int sx, int sy)
 	im->cy1 = 0;
 	im->cx2 = im->sx - 1;
 	im->cy2 = im->sy - 1;
+	im->res_x = GD_RESOLUTION;
+	im->res_y = GD_RESOLUTION;
 	im->interpolation = NULL;
 	im->interpolation_id = GD_BILINEAR_FIXED;
 	return im;
@@ -225,6 +227,8 @@ gdImagePtr gdImageCreateTrueColor (int sx, int sy)
 	im->cy1 = 0;
 	im->cx2 = im->sx - 1;
 	im->cy2 = im->sy - 1;
+	im->res_x = GD_RESOLUTION;
+	im->res_y = GD_RESOLUTION;
 	im->interpolation = NULL;
 	im->interpolation_id = GD_BILINEAR_FIXED;
 	return im;
@@ -3056,6 +3060,12 @@ void gdImageGetClip (gdImagePtr im, int *x1P, int *y1P, int *x2P, int *y2P)
 	*y2P = im->cy2;
 }
 
+void gdImageSetResolution(gdImagePtr im, const unsigned int res_x, const unsigned int res_y)
+{
+	if (res_x > 0) im->res_x = res_x;
+	if (res_y > 0) im->res_y = res_y;
+}
+
 /* convert a palette image to true color */
 int gdImagePaletteToTrueColor(gdImagePtr src)
 {

ext/gd/libgd/gd.h

@@ -253,6 +253,8 @@ typedef struct gdImageStruct {
 	int cy1;
 	int cx2;
 	int cy2;
+	unsigned int res_x;
+	unsigned int res_y;
 	gdInterpolationMethod interpolation_id;
 	interpolation_method interpolation;
 } gdImage;
@@ -433,6 +435,7 @@ void gdImageRectangle(gdImagePtr im, int x1, int y1, int x2, int y2, int color);
 void gdImageFilledRectangle(gdImagePtr im, int x1, int y1, int x2, int y2, int color);
 void gdImageSetClip(gdImagePtr im, int x1, int y1, int x2, int y2);
 void gdImageGetClip(gdImagePtr im, int *x1P, int *y1P, int *x2P, int *y2P);
+void gdImageSetResolution(gdImagePtr im, const unsigned int res_x, const unsigned int res_y);
 void gdImageChar(gdImagePtr im, gdFontPtr f, int x, int y, int c, int color);
 void gdImageCharUp(gdImagePtr im, gdFontPtr f, int x, int y, int c, int color);
 void gdImageString(gdImagePtr im, gdFontPtr f, int x, int y, unsigned char *s, int color);
@@ -746,6 +749,8 @@ int gdImagePixelate(gdImagePtr im, int block_size, const unsigned int mode);
 	of image is also your responsibility. */
 #define gdImagePalettePixel(im, x, y) (im)->pixels[(y)][(x)]
 #define gdImageTrueColorPixel(im, x, y) (im)->tpixels[(y)][(x)]
+#define gdImageResolutionX(im) (im)->res_x
+#define gdImageResolutionY(im) (im)->res_y
 
 /* I/O Support routines. */
 

ext/gd/libgd/gd_jpeg.c

@@ -195,6 +195,11 @@ void gdImageJpegCtx (gdImagePtr im, gdIOCtx * outfile, int quality)
 	cinfo.input_components = 3;	/* # of color components per pixel */
 	cinfo.in_color_space = JCS_RGB;	/* colorspace of input image */
 	jpeg_set_defaults (&cinfo);
+
+	cinfo.density_unit = 1;
+	cinfo.X_density = im->res_x;
+	cinfo.Y_density = im->res_y;
+
 	if (quality >= 0) {
 		jpeg_set_quality (&cinfo, quality, TRUE);
 	}
@@ -381,6 +386,18 @@ gdImagePtr gdImageCreateFromJpegCtxEx (gdIOCtx * infile, int ignore_warning)
 		goto error;
 	}
 
+	/* check if the resolution is specified */
+	switch (cinfo.density_unit) {
+	case 1:
+		im->res_x = cinfo.X_density;
+		im->res_y = cinfo.Y_density;
+		break;
+	case 2:
+		im->res_x = DPCM2DPI(cinfo.X_density);
+		im->res_y = DPCM2DPI(cinfo.Y_density);
+		break;
+	}
+
 	/* 2.0.22: very basic support for reading CMYK colorspace files. Nice for
 	 * thumbnails but there's no support for fussy adjustment of the
 	 * assumed properties of inks and paper. */

ext/gd/libgd/gd_png.c

@@ -120,8 +120,8 @@ gdImagePtr gdImageCreateFromPngCtx (gdIOCtx * infile)
 #endif
 	png_structp png_ptr;
 	png_infop info_ptr;
-	png_uint_32 width, height, rowbytes, w, h;
-	int bit_depth, color_type, interlace_type;
+	png_uint_32 width, height, rowbytes, w, h, res_x, res_y;
+	int bit_depth, color_type, interlace_type, unit_type;
 	int num_palette, num_trans;
 	png_colorp palette;
 	png_color_16p trans_gray_rgb;
@@ -226,6 +226,20 @@ gdImagePtr gdImageCreateFromPngCtx (gdIOCtx * infile)
 	}
 #endif
 
+#ifdef PNG_pHYs_SUPPORTED
+	/* check if the resolution is specified */
+	if (png_get_valid(png_ptr, info_ptr, PNG_INFO_pHYs)) {
+		if (png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, &unit_type)) {
+			switch (unit_type) {
+			case PNG_RESOLUTION_METER:
+				im->res_x = DPM2DPI(res_x);
+				im->res_y = DPM2DPI(res_y);
+				break;
+			}
+		}
+	}
+#endif
+
 	switch (color_type) {
 		case PNG_COLOR_TYPE_PALETTE:
 			png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);
@@ -526,6 +540,12 @@ void gdImagePngCtxEx (gdImagePtr im, gdIOCtx * outfile, int level, int basefilte
 		png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, basefilter);
 	}
 
+#ifdef PNG_pHYs_SUPPORTED
+	/* 2.1.0: specify the resolution */
+	png_set_pHYs(png_ptr, info_ptr, DPI2DPM(im->res_x), DPI2DPM(im->res_y),
+	             PNG_RESOLUTION_METER);
+#endif
+
 	/* can set this to a smaller value without compromising compression if all
 	 * image data is 16K or less; will save some decoder memory [min == 8]
 	 */

ext/gd/libgd/gdhelpers.h

@@ -42,5 +42,10 @@ int overflow2(int a, int b);
 #define gdMutexUnlock(x)
 #endif
 
+#define DPCM2DPI(dpcm) (unsigned int)((dpcm)*2.54 + 0.5)
+#define DPM2DPI(dpm)   (unsigned int)((dpm)*0.0254 + 0.5)
+#define DPI2DPCM(dpi)  (unsigned int)((dpi)/2.54 + 0.5)
+#define DPI2DPM(dpi)   (unsigned int)((dpi)/0.0254 + 0.5)
+
 #endif /* GDHELPERS_H */